Assessment of hypertension and other factors associated with the severity of disease in COVID-19 pneumonia, Addis Ababa, Ethiopia: A case-control study.

BACKGROUND: Various reports suggested that pre-existing medical illnesses, including hypertension and other demographic, clinical, and laboratory factors, could pose an increased risk of disease severity and mortality among COVID-19 patients. This study aimed to assess the relation of hypertension and other factors to the severity of COVID-19 pneumonia in patients discharged from Eka Kotebe Hospital in June-September, 2020.
METHODS: This is a single-center case-control study of 265 adult patients discharged alive or dead, 75 with a course of severe COVID-19 for the cases arm and 190 with the non-severe disease for the control arm. Three age and sex-matched controls were selected randomly for each patient on the case arm. Chi-square, multivariable binary logistic regression, and odds ratio (OR) with a 95% confidence interval was used to assess the association between the various factors and the severity of the disease. A p-value of <0.05 is considered statistically significant.
RESULTS: Of the 265 study participants, 80% were male. The median age was 43 IQR(36-60) years. Both arms had similar demographic characteristics. Hypertension was strongly associated with the severity of COVID-19 pneumonia based on effect outcome adjustment (AOR = 2.93, 95% CI 1.489, 5.783, p-value = 0.002), similarly, having diabetes mellitus (AOR = 3.17, 95% CI 1.374, 7.313, p-value<0.007), chronic cardiac disease (AOR = 4.803, 95% CI 1.238-18.636, p<0.023), and an increase in a pulse rate (AOR = 1.041, 95% CI 1.017, 1.066, p-value = 0.001) were found to have a significant association with the severity of COVID-19 pneumonia.
CONCLUSIONS: Hypertension was associated with the severity of COVID-19 pneumonia, and so were diabetes mellitus, chronic cardiac disease, and an increase in pulse rate.

Introduction

Coronavirus disease 2019 (COVID-19) is a disease caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) virus [1]. SARS-CoV-2 infection encompasses a clinical spectrum of asymptomatic infection, mild or moderate respiratory tract illness, and severe viral pneumonia with respiratory failure and even death [2]. The initial common clinical manifestations found in patients with COVID-19 included fever, cough, breathlessness, vomiting, and diarrhea [3]. The outcomes of asymptomatic to moderate COVID-19 are good, with most patients recovering with no sequelae [4]. By contrast, mortality from severe and critical cases may be as high as 50%, especially in the presence of end-organ damage and multiple-organ dysfunction syndrome [5]. Age above 65 and pre-existing medical illnesses, including hypertension, diabetes, cardiovascular disease, obesity, malignancy, chronic kidney disease, and chronic obstructive pulmonary disease, have been associated with increased morbidity and mortality [6, 7]. The prevalence of these factors in the population could help the potential burden of severe outcomes and stress on the health care system overall. Identifying clinical indicators of severe or fatal disease is necessary to enable risk stratification and optimize the allocation of limited resources.

Hypertension has been widely reported to increase the severity and mortality of patients with COVID-19. However, early COVID-19 studies have reported mixed findings concerning hypertension and other comorbidities. Findings from early studies on the association between hypertension and other comorbidities were not always adjusted for possible confounders, especially age, which has been the strongest predictor of risk for bad outcomes overall [8]. Overall, data have been inconclusive. Using logistic regression models adjusted for age and sex, some studies that conducted multivariate adjustments failed to document a significant association between hypertension and the severity of COVID-19 pneumonia [9]. On the contrary, in a larger study, hypertension was significantly associated with a 41% higher risk of mortality due to COVID-19 after adjusting for age, gender, comorbid diabetes, cerebrovascular diseases, and chronic renal disease using the Cox proportional hazard regression [10]. Of note, very few studies have examined risks for poor outcomes among persons infected with SARS-CoV-2 in sub-Saharan Africa, and in many African countries, including Ethiopia, the burden of the epidemic has appeared less than in many high-resource settings, including countries in North America and western Europe. The objective of our study was to assess the association of hypertension and other factors with the severity of COVID-19 pneumonia based on matched case-control among patients in Ethiopia, the second-largest country in Africa by population.

Method

Study area and period

This study was undertaken in Eka Kotebe General Hospital, which was the first and the only hospital in the capital, Addis Ababa, Ethiopia, dedicated as a whole to COVID-19 patients’ isolation and treatment and it is still the only center that provides dialysis/renal replacement therapy, surgical, obstetrics and gynecologic care for COVID-19 positive patients which makes it the main center for referral and admission of cases who require advanced or critical care. It has a capacity of 600 beds, with 16 beds dedicated to intensive care services. Over 130 nurses, 90 general practitioners, two internists, one anesthesiologist, two emergency physicians, one pulmonology and critical care sub-specialist, two obstetrician and gynecologists, two surgeons, two psychiatrists, two radiologists, and two pediatricians were involved in the care of those patients. Seven of these senior physicians were academic staff at Addis Ababa University, College of Health Sciences, and they have been working in the hospital since April 2020. The data collection was conducted from September to November 2021.

Source and study population

The source population was all patients admitted to the hospital with a laboratory-confirmed diagnosis of COVID-19 infection. The study population was all adult patients discharged during June-to-September 2020, before the availability of the COVID-19 vaccine at the peak of the first wave in the nation, from Eka Kotebe Hospital with severe/critical COVID-19 infection and their age (with five-year age band) and sex-matched control COVID-19 infected with mild/ moderate disease.

Study design

The study design was a case-control study. Cases were all adult RT-PCR confirmed COVID-19 patients with severe/critical disease. At the same time, controls were those age and gender-matched RT-PCR confirmed COVID-19 patients with mild/moderate disease who were also hospitalized at that time.

Inclusion criteria and exclusion criteria

Only those with symptomatic RT-PCR confirmed COVID-19 disease and discharged alive/dead from June to September 2021 were included in the study. Cases were patients aged ≥18 with severe disease. In contrast, controls were age and sex-matched patients with mild/moderate disease. Patients with severe/critical COVID-19 for whom matched control with non-severe COVID-19 patient was not available, and patients for whom severity status and/or primary outcome not documented were excluded from this study.

Sample size determination and sampling technique

The sample size was calculated using sample size determination for proportion in two populations using EPI-Info for case-control studies with an assumption of the two-sided significance level of 95%, power 80%, control to case ratio of 3 to 1, taking a proportion of hypertension among the controls of 19.6% [11] and with the assumption of the proportion to be double among the cases (39.2%). The calculated sample size was 240 using Fleiss with continuity correction. Adding 5% for incomplete data, the sample size became 252 with 63 patients on the case arm and 189 patients on the control arm. The study included all cases sequentially, and the next five consecutive non-cases for each case were included. Within the specified period of discharge times, we collected 265 patient data (75 cases and 190 controls).

Data collection techniques

Standardized case report format (CRF) was used to collect enrolled patients’ data on demographic, clinical diagnosis, laboratory, treatments, complications, and clinical outcomes from patients’ medical records at Eka Kotebe hospital. For every severe/critical COVID-19 case enrolled for data collection, we enrolled controls to be those discharged (alive or dead) on the same or immediate five days. Two independent researchers carefully reviewed the data. Discrepancies between the reviewers were resolved by discussion. Data on all variables were collected by trained physicians working at Eka Kotebe Hospital using the CRF customized and prepared by the research team.

Data quality and management

To ensure the quality of the data, training was given to data collectors in Addis Ababa for one day before the survey to ensure consistency and reduce Intra and inter-observer differences in the measurement of variables. The collected data were checked for completeness and consistency on each day of data collection. The assigned supervisors and principal investigators made supervision and monitoring every day.

Data processing and analysis

After data collection, to ensure the quality of the data, the entire filled data were checked for incompleteness and inconsistency. The extracted data on the ODK-collect server were exported directly into SPSS version 25.0 for statistical analysis. Categorical variables were presented as frequency rates and percentages (%), and continuous variables were described using a median and interquartile range. We used a chi-square test to compare exposure variables between patients with severe disease and non-severe disease groups with categorical data. Based on the results of the univariate analysis, variables with a p-value < 0.3 were selected for the multivariable binary logistic regression model. The Hosmer and Lemeshow test (p = 0.112) was used to evaluate if the binary logistic regression model was fit. Multivariable logistic regression was used to assess the association between hypertension, other demographics, and clinical factors on the severity of COVID-19 pneumonia. The model included factors associated with or borderline associated with were included in the multivariable analysis. Crude and adjusted odds ratio (OR) displayed a 95% confidence interval association. P-value < 0.05 was considered statistically significant.

Ethics approval and consent to participate

Ethical clearance was obtained from the AAU-CHS internal medicine department ethical committee and Eka Kotebe general hospital ethical review committee (approval letter with number 150/5/59). The study had no risk/negative consequence on those who participated in the study, and for the design of the study, we were not required to obtain informed consent from the participants. Medical record numbers were used for data collection, and personal identifiers were not used in the research report. The collected information was limited to the principal investigator, and confidentiality was maintained throughout.

Operational definition

SARS-CoV-2 infection was confirmed after oropharyngeal swab samples were collected and tested using RT-PCR. Hypertension was defined according to Joint National Committee 8 guideline recommendation [12]. Hypertension (HTN), also known as high blood pressure (BP), was defined as BP ≥140/90 millimeters of mercury (mmHg). It was a measure by a physician or other health care professional. Only those with an established diagnosis of hypertension at admission were included in this study. An average of five measurements was taken for each patient.

The clinical Spectrum of SARS-CoV-2 Infection was defined according to WHO and NIH COVID-19 Treatment Guideline [13, 14]. Patients with mild COVID-19 were those individuals who had any of the various signs and symptoms of COVID-19 (e.g., fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell) but who did not have shortness of breath, dyspnea, or abnormal chest imaging. Moderate COVID-19 included those with signs of lower respiratory disease during clinical assessment or imaging but who maintained a saturation of oxygen (SpO2) ≥94% on room air. Severe COVID-19 illness included individuals who had SpO2 <94% on room air at sea level, a ratio of the arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2) <300 mm Hg (SpO2/FiO2 = 315, according to Kigali definition), respiratory frequency >30 breaths/min, or infiltrates >50% of the lung parenchyma on chest imaging. Critical COVID-19 included individuals with respiratory failure, septic shock, and/ or multiple organ dysfunction. We relied on treating physician diagnosis in order to categorize patients with ARDS.

Result

A total of 265 participants were included, 75 cases and 190 controls. Two hundred twelve (80%) were males and the majority (37.7%) were in the age group 40–59, with a median age of 43 IQR (36–60) (Table 1). A statistically significant difference in some of the vital signs was found using a chi-square test among the cases and controls. These were median higher pulse rate (89 bpm vs 86 bpm P<0.003), respiratory rate (27 bpm vs 20 bpm P < 0.000), systolic blood pressure (SBP) (124 mmHg vs 118 mmHg P < 0.006), and lower oxygen saturation (SpO2) (93% vs 94% P < 0.0001) for those with severe or critical COVID-19 pneumonia (Table 2).

Table 1

Demographic characteristics of study participants.

Variables		Severity
		Non-severe disease (n = 190) (%)	Severe disease(n = 75)(%)
Age(Median, IQR):	20–39	68 (35.8)	25 (33.3)
	40–59	70 (36.8)	30 (40.0)
	≥60	52 (27.4)	20 (26.7)
Sex	Male	152 (80.0)	60 (80.0)
	Female	38 (20.0)	15 (20.0)

Table 2

Admission vital signs profile of study participants.

Variables	Severity		P-value
	Non-severe disease (n = 190)	Severe disease (n = 75)
Temperature (Median, IQR)	36.1 (36, 36.8)	36.5 (36,37)	0.068
Pulse rate (Median, IQR)	86 (79,90.2)	89 (82, 100)	0.003
Respiratory rate (Median, IQR)	20 (18, 22)	27 (24, 33)	0.000
Systolic blood pressure (Median, IQR)	118 (111,128)	124 (115,136)	0.006
Diastolic blood pressure (Median, IQR)	74 (70, 79)	75 (70, 81)	0.299
Aterial saturation (SpO2) (Median, IQR)	94 (93, 95)	93 (90, 94)	0.000

Pre-existing comorbidity was found in 35.8% of all the study participants, and 58.7% of those with severe or critical diseases. Hypertension, diabetes, and chronic cardiac and lung diseases were the most frequent comorbidities, with 19.6%, 11.3%, 4.2%, and 4.2%, respectively. COVID-19 patients with hypertension showed a significant association with severe disease (33.3%Vs14.2% p<0.01) compared with those with non-severe disease. Similarly, the presence of any comorbidity, diabetes, chronic cardiac disease, smoking, and malignancy, was all more frequent in the case group than in the control group (56.7% vs 26.8%, P<0.001; 21.3% vs 7.4% P = 0.001; 9.3% vs 2.1% P<0.05; 8.9% vs 1.5% P<0.05; and 4.0% vs 0.0% P<0.05). Regarding smoking only six (10.4%) participants reported as smokers, of which only 4 (8.9%) had severe disease, but there was no significant association with disease severity. Because there were 30.9% missed data for Body Mass Index (BMI), we could not include it in subsequent analysis. However, analysis of the available data showed there was only one (0.4%) patient with BMI≥30kg/m2 and 35(13.2%) were overweight (BMI 25–29.9kg/m2).

Fifteen (5.7%) were admitted directly to the ICU and eleven (4.2%) died from a course of severe disease while 254 (95.8%) were discharged alive (Table 3).

Table 3

Distribution of comorbidities, disease severity, and outcome of study participants.

Variables		Severity		X2	P-value
		Non-severe disease (n = 190)	Severe disease (n = 75)
Comorbidity	Yes	51 (26.8)	44 (58.7)	23.6	0.000
	No	139 (73.2)	31 (18.2)
Hypertension	Yes	27 (14.2)	25 (33.3)	12.4	0.000
	No	163 (85.8)	50 (66.7)
Diabetic mellitus	Yes	14 (7.4)	16 (21.3)	10.4	0.001
	No	176 (92.6)	59 (78.7)
Chronic pulmonary disease	Yes	8 (4.2)	3 (4.0)	0.0	1.000
	No	182 (95.8)	72 (96.0)
Chronic cardiac disease	Yes	4 (2.1)	7 (9.3)	7.0	0.014
	No	186 (97.9)	68 (90.7)
HIVa	Yes	6 (3.2)	4 (5.3)	0.7	0.585
	No	182 (95.8)	70 (93.3)
	Unknown	2 (1.1)	1 (1.3)
Smoking	Yes	2 (1.5)	4 (8.9)	5.6	0.018
	No	131 (98.5)	41 (91.1)
Tuberculosis	Yes	2 (1.1)	2 (2.7)	0.9	0.318
	No	188 (98.9)	73 (97.3)
Malignancy	Yes	0 (0.0)	3 (4.0)	7.6	0.022
	No	190 (100.0)	72 (96.0)
CKDb	Yes	0 (0.0)	2 (2.7)	5.1	0.079
	No	190 (100.0)	73 (97.3)
Direct ICU admission	Yes	0 (0.0)	15 (20)	40.2	0.000
	No	190 (100.0)	60 (80.0)
Outcome	Discharged	190 (100.0)	64 (85.3)	29.0	0.000
	Death	0 (0.0)	11 (14.7)

a-Human immunodeficiency virus

b-Chronic kidney disease.

As shown in Table 4, there were some missing data for most laboratory findings where its percentage difference among the study groups and for laboratory tests ranging from 2.7% to 9.3% for the cases. However, after removing all missing data from each variable, the median value and proportion were compared with disease severity, and white cell (WBC) count, absolute lymphocyte count (ALC), Neutrophil-lymphocyte ratio (NLR), platelet count, Alanine Transaminase (ALT), Aspartate transaminase (AST), and urea were found to have significant association with disease severity. On the categorical analysis of the laboratory markers, those who had severe disease had significant leukocytosis (> 10,000 cells/ μL) (30.1% vs 9.8% p < 0.002); lymphopenia (<1000 cells/ μL) (63% vs 21.6% p < 0.000); raised neutrophil-to-lymphocyte ratio of ≥ 10 (28.8% vs 8.8% p < 0.001); thrombocytopenia (<150,000 cells/ μL) (16.4% vs 5% p < 0.013); elevated ALT (35.7% vs 14.1% p < 0.001); elevated AST (76.5% vs 28.1% p < 0.0001); and elevated urea (31.9% vs 16.5% p < 0.025) compared to those who had non-severe disease.

Table 4

Distribution of laboratory values and disease severity of study participants.

Variables		Severity		X2	P-
		Non-severe disease	Severe disease		value
Haemoglobin g/dl (Median, IQR) n = 173		14.3 (13,15.8)	14 (12.8, 15.1)		0.196
	<12	7 (3.7)	10(14.1)	2.4	1.16
	≥12	95 (93.1)	61 (85.9)
WBCa 103count cells/μL (Median, IQR) n = 175		5.83 (5.14,7.19)	7.74 (5.38,10.6)		0.000
	<4	11 (10.8)	4 (5.5)	12.3	0.002
	4–10	81 (79.4)	47 (64.4)
	≥ 10	10 (9.8)	22 (30.1)
ALCb 103 count cells/μL (Median, IQR) n = 175		1400 (1088.2,1643)	845 (535,1222.2)		0.000
	< 1000	22 (21.6)	46 (63.0)	30.7	0.000
	≥ 1000	80 (78.4)	27 (37.0)
NLRc (Median, IQR) n = 175		3 (2.0,3.2)	7.2 (3.8,11.4)		0.000
	< 10	93 (91.2)	52 (71.2)	11.9	0.001
	≥ 10	9 (8.8)	21 (28.8)
Platelet (Median, IQR) n = 173		223,500 (191,250–279,000)	223,000 (160,000–335,500)		0.972
	Yes	5 (5.0)	12 (16.4)	6.2	0.013
	No	95 (95.0)	61 (83.6)
ALTd (Median, IQR) n = 162		29 (22, 41)	42 (34.7, 74.7)		0.000
	< 60	79 (85.9)	45 (64.3)	10.3	0.001
	≥ 60	13 (14.1)	25 (35.7)
ASTe (Median, IQR) n = 157		25 (20, 38)	51.5 (38, 62.5)		0.000
	< 37	64 (71.9)	16 (23.5)	36.1	0.000
	≥ 37	25 (28.1)	52 (76.5)
Urea (Median, IQR) n = 154		13 (10, 17)	17 (12, 23)		0.003
	< 20	71 (83.5)	47 (68.1)	5.0	0.025
	≥ 20	14 (16.5)	22 (31.9)
Creatinine (Median, IQR) n = 162		0.83 (0.68, 1.04)	0.87 (0.74, 1.02)		0.113
	< 1.2	85 (93.4)	61 (85.9)	2.5
	≥ 1.2	6 (6.6)	10 (14.1)

a-WBC-white cell count,

b-Absolute lymphocyte count,

c-Neutrophil lymphocyte count,

d-Alanintransaminase,

e-Aspartatetransaminase.

In addition to isolation and monitoring, different treatment armaments were used based on the severity and complications of the illness. Antibiotics, systemic anticoagulants, dexamethasone, prone positioning, vasopressor were most frequently used interventions, 40.4%, 31.3%, 29.1%, 19.6% and 2.6% respectively. For those with non-severe COVID-19 only antibiotics (16.8%) and anticoagulants (4%) were given from the list of interventions mentioned in Table 5. The rest of the interventions were given solely to those with severe diseases, indicating the interventions were not given or used in equal proportions in both groups. A therapeutic dose of anticoagulant was used in 36(13.6%) and experimental agents in 3(1.1%) patients, 2 were given hydroxychloroquine and 1 took remdesivir. Most observed complications were pneumonia in 24.4%, acute respiratory distress syndrome (ARDS) in 5.3%, acute kidney injury (AKI) in 4.9%, bacteremia in 3.4%, cardiac arrest in 3.4%, and shock in 3% of those with severe disease (Table 5).

Table 5

Treatment and complications of study participants.

Variables		n (%)	Variables		n (%)
IV fluid	Yes	21 (7.9)	Complications
	No	244 (92.1)	Shock	Yes	8 (3.0)
Corticosteroids	Yes	75 (28.3)		No	257 (97.0)
	No	190 (71.7)	Meningitis/Encepha litis	Yes	2 (0.8)
Antibiotics	Yes	107 (40.4)		No	262 (98.9)
	No	158 (59.6)	Cardiac arrhythmia	Yes	6 (2.3)
Antifungal	Yes	4 (1.5)		No	259 (97.7)
	No	261 (98.5)	Cardiac arrest	Yes	9 (3.4)
Experimental agent	Yes	3 (1.1)		No	256 (96.6)
	No	262 (98.9)	Pneumonia	Yes	64 (24.2)
Systemic anti-coagulant	Yes	83 (31.3)		No	201 (75.8)
	No	182 (68.7)	ARDS	Yes	14 (5.3)
Patters of anti-coagulant	Therapeutic	36 (13.6)		No	251 (94.7)
	Prophylactic	47 (17.7)	Bacteraemia	Yes	9 (3.4)
Oxygen therapy	Yes	75 (28.3)		No	256 (96.6)
	No	190 (71.7)	Acute renal injury	Yes	13 (4.9)
Prone	Yes	52 (19.6)		No	252 (95.1)
	No	7 (2.6)	Liver dysfunction	Yes	5 (1.9)
	Unspecified	16 (6.0)		No	260 (98.1)
Vasopressors	Yes	7 (2.6)	Cardiomyopathy	Yes	1 (0.4)
	No	258 (79.4)		No	264 (99.6)

Hypertension, pulse rate, respiratory rate, SBP, SpO2, comorbidity, diabetes, and chronic cardiac disease were all significantly associated with disease severity on univariate analysis. On the multivariable binary logistic regression analysis (adjusted odds ratio) with the omission of respiratory rate from this final analysis model, hypertension was associated with disease severity (AOR = 2.93, 95% CI 1.489, 5.783, p-value = 0.002). Furthermore, an increase in pulse rate, diabetes mellitus, and chronic cardiac disease were also significantly associated with COVID-19 pneumonia severity.

As the pulse rate increased by one beat per minute, the likelihood of the disease becoming severe increased by 1.04 times (AOR = 1.041, 95% CI 1.017, 1.066, p-value = 0.001). Again, patients with diabetes have a 3.1-fold increased likelihood of having the severe disease when compared to non-diabetic patients (AOR = 3.17, 95% CI 1.374, 7.313, p-value<0.007), and those with chronic cardiac disease 4.8-fold increased tendency to have severe disease (AOR = 4.803, 95% CI 1.238–18.636, p<0.023) (Table 6).

Table 6

Determinants of disease severity.

Variables	COR (95% CI)	P-value	AOR* (95% CI)	p-value
Pulse rate	1.036 (1.013–1.060)	0.002	1.041 (1.017–1.066)	0.001
Hypertension
Yes	3.019 (1.608–5.665)	0.001	2.934 (1.489–5.783)	0.002
No	1		1
Diabetes Mellitus
Yes	3.409 (1.570–7.404)	0.002	3.170 (1.374–7.313)	0.007
No	1		1
Chronic cardiac disease
Yes	4.787 (1.358–16.867)	0.015	4.803 (1.238–18.636)	0.023
No	1		1

*Adjusted odds ratio(AOR) after the respiratory rate was removed or omitted from the final model for its mediator effect.

Discussion

We assessed the association between the severity of COVID-19 pneumonia and the demographic, clinical, and laboratory profile of discharged alive or dead patients. The chi-square result showed a significant difference in vital signs and comorbidities among patients with non-severe and severe diseases. This association showed that the severe disease group had had higher respiratory rate, pulse rate, systolic blood pressure, lower SPO2, one or more comorbid illnesses, had hypertension, diabetes mellitus, chronic cardiac and pulmonary diseases; and, lower ALC, higher NLR, relatively lower platelet count and raised ALT, AST, and urea. This change in vital status suggests the possible contribution of demographic and clinical characteristics to disease severity.

The univariate analysis has shown pulse rate, respiratory rate, SBP, SpO2, presence of any comorbidity, hypertension, diabetes mellitus, and chronic cardiac disease were significantly associated with the severity of the disease, indicating that these factors independently contributed to the severity of COVID-19 pneumonia. After controlling other covariates upon further analysis using multivariate binary logistic regression, especially removing the respiratory rate from the final model for its mediator effect on disease severity (upon assessment for bivariate collerate and multicollinear effect, respiratory rate was the only variable with a strong modifying effect on the association of hypertension and other factors on the severity of COVID-19 pneumonia), hypertension showed a significant association to disease severity, as it has shown a significant association on univariate logistic regression. Hypertension was the most prevalent comorbidity in COVID-19 patients; estimated prevalence rates ranged from 15.0% to 36.5% [9, 15]. Some associations between hypertension and the severity of the COVID-19 illness were suggested earlier during the pandemic. HE Abraha et al., Jean B. Nachega et al., Guan WJ et al., and Wang D et al. reported a 24.6%, 24.5%, 23.7%, and 58.3% prevalence rate of hypertension among patients with severe COVID-19 pneumonia, respectively [1, 12, 16, 17].

Our results are consistent with systematic reviews and meta-analyses indicating that hypertension was the most prevalent chronic morbidity in COVID-19 patients [17%; 95% confidence interval (CI):14–22%]. One meta-analysis showed that the odds (OR) of hypertension in patients with severe disease, in comparison to those with non-severe disease, was 3.42 (95%CI: 1.88–6.22) [18, 19]. One of the early pieces of evidence during the pandemic, a retrospective case study from china, showed that a quarter of patients had at least one comorbidity. The most prevalent comorbidity was hypertension (16.9%), followed by diabetes (8.2%), with an increased risk for severe disease by 1.6-fold and 1.6-fold, respectively. Those with two or more comorbidities were 2.5 times at risk for a severe and fatal course of the disease [19].

In one particular retrospective study in Lagos, Nigeria with a total of 2075 adult COVID-19 cases, the prevalence of hypertension was 17.8% followed by diabetes (7.2%). Hypertension posed an increased risk (approx. 4-fold) of severe COVID-19 in the presence of multiple comorbidities [7]. A meta-analysis also showed that hypertension was significantly associated, nearly 1.5 times, with the increased risk of adverse outcomes in COVID-19 patients. The subgroup analysis with an adjusted odds ratio showed a significant correlation between hypertension and adverse outcomes [20]. From the pooled analysis performed on 13 studies with a total of 2893 COVID-19 patients hypertension was found to be associated with a nearly 2.5-fold significantly enhanced risk of severe COVID-19 disease [21]. Because the association of hypertension with the adverse outcomes of COVID-19 patients might be affected by various factors such as age, gender, and other comorbidities, it is recommended to have adjusted effect estimates for confounders before we concluded which we did in our study.

Similarly, diabetes mellitus, chronic cardiac disease, and pulse rate were also factors significantly associated with the severity of the disease. Having diabetes mellitus was found to be an important predictor of disease severity. Especially if the diabetes is poorly controlled, it is known to lead to compromised immunity that decreases the body’s ability to clear infections, including SARS-CoV2 infection. And has a high chance of having additional chronic illness than non-diabetic patients. Diabetes mellitus has rapidly become established as a major co-morbidity for severe COVID-19 disease. It is believed that diabetic individuals are not more susceptible to developing viral infection per se but are more likely to show increased clinical severity and to require ICU admission. Body mass index was independently associated with adverse outcomes in COVID-19 patients with diabetes [22]. Hyperglycemia, altered immune function, sub-optimal glycaemic control during admission, reduced forced vital capacity, and pro-thrombotic and pro-inflammatory state makes them vulnerable to severe and critical illness with complications [23, 24]. This is consistent with reports of association with severe COVID-19 pneumonia and poor prognosis from other counties [25-28] and local studies [29].

In a meta-analysis of eight studies, cardiovascular disease was one of the most prevalent co-morbidities following hypertension and diabetes [18], also shown in a meta-analysis by Wang et al. [30] and Huang et al. [2]. Compared to patients with non-severe disease, the pooled odds ratio of cardiovascular disease in severe cases was 3.42, closer to our study finding [18]. From the first systematic review and meta-analysis focusing on the relationship of severe COVID-19 with cardiovascular disease and its risk factors, the majority of studies showed a positive association between prior chronic cardiac disease and severe COVID-19, with the primary pooled relative risk of 5.05 and the pooled adjusted relative risk estimate was 1.75, where it is accounted for confounders especially age [31].

The explanation for the higher prevalence of hypertension, diabetes mellitus, and cardiac disease among COVID-19 patients may focus on the SARS-CoV-2 cell entry mechanism. Similar to SARS-CoV-1, SARS-CoV-2 contains a receptor-binding domain (RBD) that recognizes angiotensin-converting enzyme 2 (ACE2) as its receptor with a higher binding affinity compared to SARS-CoV-1 [32]. Epithelial cells of the lungs, intestine, kidney, and blood vessels are identified to have abundant ACE2 receptors [33]. Hence, increased expression of ACE2 may promote the internalization of SARS-CoV-2, which in turn may increase the chances of developing COVID-19 or a severe form of the disease [34]. The severity of COVID-19 among patients with hypertension, diabetes, and chronic cardiac disease also may be partially explained by the increased incidence of thrombotic complications which is a fact that patients with these conditions are at increased risk of thrombotic events [35, 36]. These chronic medical conditions often present with inflammation and weakened innate immune responses in affected individuals. This may predispose those individuals to infections and disease complications [18]. The high prevalence of fatal cases among COVID-19 patients with hypertension, diabetes, and chronic cardiac disease as comorbidity could be due to the induction of cytokine storm. Cytokine storms resulting in hyper-inflammation are the hallmarks of severe SARS-CoV-2 infection [37]. Metabolic inflammation as a consequence of hypertension, diabetes, and chronic cardiac disease is also known to compromise the immune system. These patients are commonly reported to have weakened immunological function arising from reduced macrophage and lymphocyte activity which could predispose individuals to infections, especially those infections for which cell-mediated immunity constitutes an important host defense [38].

Furthermore, the study showed that a single increase in pulse rate is one of the factors for having severe or critical COVID-19 pneumonia. An increase in pulse rate indicates a cardiorespiratory or metabolic disease, resulting in a poor prognosis. An increase in heart rate, and even more variability, have been related to worse outcomes in infection [39]. The therapeutic trial to lower it in septic patients has not been associated with an improvement in cardiac function [40] nor with the amelioration of mortality risk [41]. From this evidence, one could speculate that heart rate in infection is simply a marker of a severe clinical condition and a response to sepsis at presentation. However, others believe it could be related to the emergence of autonomic dysfunction [42]. In a patient with COVID-19, the persistence of increased heart rate has been assumed to be related to a dysregulation of an autonomic system [43]. A heart rate higher than 100 beats per minute has also been inserted into the latest European guidelines on hypertension as a prognostic marker since it is related to future cardiovascular events [44]. Discharge heart rate is strongly related to the evidence of a severe disease defined as the need for ICU admission and/or mechanical ventilation. The increase in heart rate at discharge was almost four times higher in patients with severe disease than in patients without severe disease (15.2% vs. 4%) [45]. Some clinicians are interested more in the persistence of sinus tachycardia over time with symptoms that could remain for longer than 3 weeks [46].

The other relevant factors identified in most studies are deranged laboratory parameters of WBC, ALC, NLR, platelet count, ALT, AST, and urea, [26, 27, 47, 48]. Though the data were incomplete for some of our cases and controls, it had shown an association with the disease severity on the chi-square test.

Most notably, similar to other local and regional [7, 17] studies our findings showed that the majority of study participants including those with severe diseases were young, however, only nearly one-third of the participants had comorbidity which was slightly lower than other local studies [29]. Interestingly, lower mortality rates are reported in most African countries compared to the global trend, unlike in Europe and the USA [49-52]. Though the reason is not fully understood, it is postulated that it could be related to warmer weather and the predominant youth population [52]. However, our finding showed an association between some comorbidities and disease severity among Ethiopian patients which could be also the case in other African patients as there is an epidemiological transition in a rise of non-communicable diseases in sub-Saharan Africa [53]. Earlier reports from the UK showed increased mortality among ethnic minorities where the exact explanations were not clear, but it was believed to be due to biological, medical, or sociological factors [54, 55]. Given the known risk factors for COVID-19 complications, the confluence of hypertension, diabetes, obesity, and the higher prevalence of cardiovascular disease among black persons may be driving these early signals. Among the two most populous countries in Africa, Nigeria and Ethiopia, the national prevalence of hypertension is 28.9% and 19.6% and diabetes mellitus is 5.77% and 5%, respectively [11, 56–58]. And where there is a lack of awareness and poor health-seeking behavior in our population, many patients present with uncontrolled diseases with attending complications which could contribute to the severity of their illness [59].

Strength and limitation

The main strength of this study was the enrolment of patients with COVID-19 confirmed by RT-PCR from a dedicated treatment center where the admission protocol and case management were consistent. It was also a matched study with an enrollment of subsequent cases for the controls discharged in the nearest one week. However, this study had a few limitations. First, the strict matching criteria, including the date of discharge on selecting one case for three controls, failed to fulfill the planned case-to-control ratio, we collected data for 75 cases for which we were supposed to collect proportionally 225 controls which makes the total sample size to be 300. However, we were able to retrieve data of 75 cases for 190 controls which made the total sample size 265, which is a bit higher than the initial calculated sample size (252, 63 cases for 189 controls) with a slightly higher number of those on case arm (75 vs 63). Furthermore, data were missing due to the study’s retrospective nature, thus affecting detailed analyses of factors that may impact the severity of the disease. And thus, incomplete data on vital signs, behavioral and comorbidity documentation, and key laboratory tests limited the power of association analyses. In addition, the number of patients with some specific comorbidities was too small to conclude that such diseases, particularly CKD and malignancy, do not influence the severity of COVID-1.

Conclusion

Hypertension was strongly associated with the severity of COVID-19 pneumonia based on effect outcome adjustment. And also, an increase in pulse rate, diabetes mellitus, and chronic cardiac disease was strongly associated with the severity of the disease. A single increase in pulse rate should alert the triage or treating team for early anticipation of a high chance of progressing to severe or critical disease and close monitoring for pulse rate. We also advise strict infection prevention and a low threshold for early detection, management, and anticipation of adverse outcomes among patients with hypertension, diabetes mellitus, and chronic cardiac disease.

15 Mar 2022

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Additional Editor Comments:

Although reviewers have found this study interesting they have raised some significant questions. The major concern is about the novelty of this study as raised by Reviewer 3. In addition to addressing other comments raised by reviewers, please specifically and categorically explain in the manuscript about how this study is different than what published by Leulseged et al, 2022.

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Reviewer #1: This is an excellent report based on very thorough research. The members of research team ensured that the manuscript adheres to high ethical standards. Overall, this is a concise and well-written manuscript. The introduction is relevant and theory-based. The authors have included sufficient information about the previous studies in the discussion section, which will aid readers in following the rationale and procedures of the present study. The data of the manuscript contributes in understanding of COVID-19 related comorbidities and thy significant for understanding COVID associated disease aetiology.

However, the following points should be considered in the present form of this manuscript.

• In result section of the manuscript, the authors have reported positive association between many clinical characteristics and COVID associated Comorbidities. In discussion section the authors have mention about the findings. In my view authors should discuss about the possible pathological features by which mentioned clinical characteristics can contribute in disease severity. This will aid readers to follow the rationale of the study. (Note: Authors should to relate the results from the studies referring SARS-Cov and MERS-CoV which are structurally similar to COVID19 virus. Just reference to study which are associates demographic and clinical characteristics with viral disease severity should be good enough)

• In my view, authors should also consider applicability of Cox proportional hazard model (CH Model) for the association of various clinical indices and vital signs with the COVID abide severity because of following points:

CH model Adjusts multiple risk factors simultaneously.

• CH model also aid to limit the number of strata.

• Provides estimates and confidence intervals of how the risk changes (Clinical characteristics) across the strata and across unit increases the quantitative variables

• The severity of the viral disease also showed significant differences based on ethnicity and demography of the population, In my view, authors have reported associated between various clinical indices and disease severity in a African population. This may aid in understanding physiological parameter which resulted in heavy COVID severity in the African population and also hold population centric translational significance. So, I would suggest authors to add this crucial suggestion in discussion part of the manuscript.

Minor comments:

• Authors should rewrite the results section to ensure the result section looks well connected and free from any grammatical errors.

• Please sure that ethical protocol approval number and certificate should be incorporated in the supplementary data alongside a sample consent form approved by the ethical committee.

Reviewer #2: The data presented in the manuscript is collected from the patients admitted with severe/non-severe COVID-19 disease at the Eka Kotebe General Hospital, COVID-19 Isolation and Treatment Center. The treatment regimen remained standard within the study group. The manuscript is well written with statistically significant evaluation of the comorbidities associated with COVID-19.

Reviewer #3: This is an association study between different risk factors with the severity of COVID-19 pneumonia in patients. The study included 265 severe COVID-19 and 190 with the non-severe disease. While the data is interesting, the manuscript has significant omissions. My primary concerns are the following:

- Recent publication from Leulseged et al, 2022 “COVID-19 disease severity and associated factors among Ethiopian patients: A study of the millennium COVID-19 care center” have performed similar study in Ethiopian population in 686 patients. Can authors address how their study is different from this recent publication?

- The key problem with this study is that in the complex phenotype field, few researchers would have confidence in an association that is based on these small sample sizes. (Even if the authors stated as the power of the study).

- The discussion could be made much more interesting. As it is, they primarily reiterate their results and provide a bit more literature review. However, it would be interesting if they could discuss clinical implications and areas for further study.

**********

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22 Apr 2022

Academic editor comments

Journal Requirements:

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming.

Response: Thank you for the comment and we edited the manuscript as to PLOS ONE journal requirements. The revisions we made are:

a) The title, headings, and subsection were edited to sentence case with their respective level font size.

b) The affiliation of the authors was corrected as to the guideline; department and city were included.

c) We removed the authors' declaration, contribution, funding, and conflicts of interest section, as it is well illustrated with the track change.

d) The ethics statement is moved to the Methods section

e) The references are cited in the main text in brackets and are edited according to the journal guidelines, for references with more than six authors the first six author names are listed followed by “et al.”

2. Please amend either the title on the online submission form (via Edit Submission) or the title in the manuscript so that they are identical.

Response: Thank you for the suggestion.

Full title from online submission form: ‘Assessment of Hypertension and Other Factors Associated with Severity of Disease in COVID-19 Pneumonia, Addis Ababa, Ethiopia: A Case-Control Study’ (Short Title: Risk Factors associated with Severity of COVID-19)

Title in the manuscript: ‘Assessment of hypertension and other factors associated with the severity of disease in COVID-19 pneumonia, Addis Ababa, Ethiopia: a case-control study ’

Apart from the edition of title to sentence case for the title in the manuscript, there was the omission of an article ‘the’ from the one written on the online submission. So, we amend that the title in the manuscript is the correct one and we will also edit accordingly.

3. Your ethics statement should only appear in the Methods section of your manuscript. If your ethics statement is written in any section besides the Methods, please move it to the Methods section and delete it from any other section. Please ensure that your ethics statement is included in your manuscript, as the ethics statement entered into the online submission form will not be published alongside your manuscript.

Response: Thank you for the comment and it is well amended. It is removed and incorporated in the Methods section accordingly (as depicted with track change)

Additional Editor Comments:

Although reviewers have found this study interesting they have raised some significant questions. The major concern is about the novelty of this study as raised by Reviewer 3. In addition to addressing other comments raised by reviewers, please specifically and categorically explain in the manuscript about how this study is different than what published by Leulseged et al, 2022.

Response: Thanks for the concern raised.

We are aware of the recent report from the Millennium Center, which has conclusions that are similar to our study. However, we feel that our paper adds to the literature in a significant manner. Ethiopia is the second-largest country in Africa by population, with some 115 million people, and a single report from a single center simply cannot suffice to describe any aspect of Covid-19 completely. Our study reports a cohort independent from the prior study, with a different methodology. Even if the results are somewhat similar, these are valuable and novel data.

Our study aimed to show mainly the association between hypertension and severity of COVID-19 pneumonia, and we also assessed the relation with other comorbidities, clinical, and laboratory characteristics of patients admitted at Eka General Hospital, which was the first and the only hospital in the capital dedicated as a whole for COVID-19 patients isolation and treatment and it is still the only center that provides dialysis/renal replacement therapy, surgical, obstetrics and gynecologic care for COVID-19 positive patients which makes it the main center for referral and admission of cases who require advanced or critical care. We compared differences between those with non-severe (mild/moderate COVID-19) to those with severe (severe/critical COVID-19) diseases, which we considered a matched case-control design to show an association. Whereas, Leulseged et al, 2022 study assessed COVID-19 patients admitted to Millunium COVID-19 Care Center (MCCC), the other care center in the capital which was a repurposed field hospital from a multipurpose recreation/exhibition center, for any characteristics associated with COVID-19 severity. They conducted a cross-sectional study on all selected patients of all age groups. Regarding ours, it was a matched case-control study, where cases were all adult RT-PCR confirmed COVID-19 patients with severe/critical disease. At the same time, controls were those age and gender-matched RT-PCR confirmed COVID-19 patients with mild/moderate disease who were discharged within the study period.

Furthermore, the other difference was sample size determination and sampling technique, they determined it using a double population proportion formula with the assumptions of; a 95% confidence interval, power of 80%, the proportion of males who had the severe disease as 80%, the proportion of females who had the severe disease as 75% and considering a non-response rate of 10%, using a simple random sampling technique. In our study, the sample size determination was based on the assumption of the two-sided significance level of a 95%, power of 80%, control to case ratio of 3 to 1, taking a proportion of hypertension among the controls to be 19.6% (inferred from the population-based study) and with the assumption of the proportion to be double among the cases (39.2%). The study included all cases sequentially, and the next five consecutive non-cases for each case were included (which were age and gender-matched).

Despite the above difference, we learned a lot from their study and tried to improve some aspects of our association study. Notably, we decided to match the participants for important demographic characteristics and to omit clinical characteristics that had pathobiological or effect-modifying relation with a severe manifestation of a disease (in our case we omitted such potential modifiers after checking for bivariate collerate and multicollinear effect).

In our study, the association assessment was focused on a specific factor or variable mainly (hypertension) as an entry with patients grouped as severe and non-severe, whereas the Leulseged et al. 2022 tried to show association assessment with several factors across the severity spectrum of COVID-19 (mild, moderate, severe) separately in addition to the difference in the study population, sample size determination, and sampling technique.

Reviewers' comments:

Reviewer #1: This is an excellent report based on very thorough research. The members of research team ensured that the manuscript adheres to high ethical standards. Overall, this is a concise and well-written manuscript. The introduction is relevant and theory-based. The authors have included sufficient information about the previous studies in the discussion section, which will aid readers in following the rationale and procedures of the present study. The data of the manuscript contributes in understanding of COVID-19 related comorbidities and thy significant for understanding COVID associated disease aetiology.

However, the following points should be considered in the present form of this manuscript.

1)• In result section of the manuscript, the authors have reported positive association between many clinical characteristics and COVID associated Comorbidities. In discussion section the authors have mention about the findings. In my view authors should discuss about the possible pathological features by which mentioned clinical characteristics can contribute in disease severity. This will aid readers to follow the rationale of the study. (Note: Authors should to relate the results from the studies referring SARS-Cov and MERS-CoV which are structurally similar to COVID19 virus. Just reference to study which are associates demographic and clinical characteristics with viral disease severity should be good enough)

Response: Thank you, that is important and incorporated in the discussion section.

-In paragraph 7 of the Discussion section:

The explanation for the higher prevalence of hypertension, diabetes mellitus, and cardiac disease among COVID-19 patients may focus on the SARS-CoV-2 cell entry mechanism. Similar to SARS-CoV-1, SARS-CoV-2 contains a receptor-binding domain (RBD) that recognizes angiotensin-converting enzyme 2 (ACE2) as its receptor with a higher binding affinity compared to SARS-CoV-1 [32]. Epithelial cells of the lungs, intestine, kidney, and blood vessels are identified to have abundant ACE2 receptors [33]. Hence, increased expression of ACE2 may promote the internalization of SARS-CoV-2, which in turn may increase the chances of developing COVID-19 or a severe form of the disease[34]. The severity of COVID-19 among patients with hypertension, diabetes, and chronic cardiac disease also may be partially explained by the increased incidence of thrombotic complications which is a fact that patients with these conditions are at increased risk of thrombotic events [35,36]. These chronic medical conditions often present with inflammation and weakened innate immune responses in affected individuals. This may predispose those individuals to infections and disease complications [37]. The high prevalence of fatal cases among COVID-19 patients with hypertension, diabetes, and chronic cardiac disease as comorbidity could be due to the induction of cytokine storm. Cytokine storms resulting in hyper-inflammation are the hallmarks of severe SARS-CoV-2 infection [38]. Metabolic inflammation as a consequence of hypertension, diabetes, and chronic cardiac disease is also known to compromise the immune system. These patients are commonly reported to have weakened immunological function arising from reduced macrophage and lymphocyte activity which could predispose individuals to infections, especially those infections for which cell-mediated immunity constitutes an important host defense [39].

2)• In my view, authors should also consider applicability of Cox proportional hazard model (CH Model) for the association of various clinical indices and vital signs with the COVID abide severity because of following points:

CH model Adjusts multiple risk factors simultaneously.

• CH model also aid to limit the number of strata.

• Provides estimates and confidence intervals of how the risk changes (Clinical characteristics) across the strata and across unit increases the quantitative variables

Response: Thank you for the comment and suggestion. Because we were primarily interested in the effect of hypertension, a widely reported risk for poor outcomes in patients with Covid-19 illness, we chose to perform multivariable binary regression. We agree with the reviewer that using a Cox proportional hazards approach could also be informative for looking at a multiplicity of risks, and we will perhaps plan to perform such an analysis in a later study

3)• The severity of the viral disease also showed significant differences based on ethnicity and demography of the population, In my view, authors have reported associated between various clinical indices and disease severity in a African population. This may aid in understanding physiological parameter which resulted in heavy COVID severity in the African population and also hold population centric translational significance. So, I would suggest authors to add this crucial suggestion in discussion part of the manuscript.

Response: Thank you for this vital comment and it is incorporated.

In paragraph 10 of the Discussion section:

Interestingly, lower mortality rates are reported in most African countries compared to the global trend, unlike in Europe and the USA [50,51,52,53]. Though the reason is not fully understood, it is postulated that it could be related to warmer weather and the predominant youth population[53]. However, our finding showed an association between some comorbidities and disease severity among Ethiopian patients which could be also the case in other African patients as there is an epidemiological transition in a rise of non-communicable diseases in sub-Saharan Africa[54]. Earlier reports from the UK showed increased mortality among ethnic minorities where the exact explanations were not clear, but it was believed to be due to biological, medical, or sociological factors[55,56]. Given the known risk factors for COVID-19 complications, the confluence of hypertension, diabetes, obesity, and the higher prevalence of a cardiovascular disease among black persons may be driving these early signals. Among the two most populous countries in Africa, Nigeria and Ethiopia, the national prevalence of hypertension is 28.9% and 19.6% and diabetes mellitus is 5.77% and 5%, respectively[57,11,58,59]. And where there is a lack of awareness and poor health-seeking behavior in our population, many patients present with uncontrolled diseases with attending complications which could contribute to the severity of their illness[60].

Minor comments:

a)• Authors should rewrite the results section to ensure the result section looks well connected and free from any grammatical errors.

Response: Thank you for the comment. We edited the grammatical errors and tried to give it a better flow (as well illustrated in track changes).

b)• Please sure that ethical protocol approval number and certificate should be incorporated in the supplementary data alongside a sample consent form approved by the ethical committee.

Response: We incorporated the protocol number in the main text Methods section and the supplementary information section. But for the consent form due to the retrospective nature of our study, we were granted a waiver and we didn’t use one.

Reviewer #2: The data presented in the manuscript is collected from the patients admitted with severe/non-severe COVID-19 disease at the Eka Kotebe General Hospital, COVID-19 Isolation and Treatment Center. The treatment regimen remained standard within the study group. The manuscript is well written with statistically significant evaluation of the comorbidities associated with COVID-19.

Response: Thank you for the comment.

Reviewer #3: This is an association study between different risk factors with the severity of COVID-19 pneumonia in patients. The study included 265 severe COVID-19 and 190 with the non-severe disease. While the data is interesting, the manuscript has significant omissions. My primary concerns are the following:

-1) Recent publication from Leulseged et al, 2022 “COVID-19 disease severity and associated factors among Ethiopian patients: A study of the millennium COVID-19 care center” have performed similar study in Ethiopian population in 686 patients. Can authors address how their study is different from this recent publication?

Response: Thanks for the concern raised.

We are aware of the recent report from the Millennium Center, which has conclusions that are similar to our study. However, we feel that our paper adds to the literature in a significant manner. Ethiopia is the second-largest country in Africa by population, with some 115 million people, and a single report from a single center simply cannot suffice to describe any aspect of Covid-19 completely. Our study reports a cohort independent from the prior study, with a different methodology. Even if the results are somewhat similar, these are valuable and novel data.

Our study aimed to show mainly the association between hypertension and severity of COVID-19 pneumonia, and we also assessed the relation with other comorbidities, clinical, and laboratory characteristics of patients admitted at Eka General Hospital, which was the first and the only hospital in the capital dedicated as a whole for COVID-19 patients isolation and treatment and it is still the only center that provides dialysis/renal replacement therapy, surgical, obstetrics and gynecologic care for COVID-19 positive patients which makes it the main center for referral and admission of cases who require advanced or critical care. We compared differences between those with non-severe (mild/moderate COVID-19) to those with severe (severe/critical COVID-19) diseases, which we considered a matched case-control design to show an association. Whereas, Leulseged et al, 2022 study assessed COVID-19 patients admitted to Millunium COVID-19 Care Center (MCCC), the other care center in the capital which was a repurposed field hospital from a multipurpose recreation/exhibition center, for any characteristics associated with COVID-19 severity. They conducted a cross-sectional study on all selected patients of all age groups. Regarding ours, it was a matched case-control study, where cases were all adult RT-PCR confirmed COVID-19 patients with severe/critical disease. At the same time, controls were those age and gender-matched RT-PCR confirmed COVID-19 patients with mild/moderate disease who were discharged within the study period.

Furthermore, the other difference was sample size determination and sampling technique, they determined it using a double population proportion formula with the assumptions of; a 95% confidence interval, power of 80%, the proportion of males who had the severe disease as 80%, the proportion of females who had the severe disease as 75% and considering a non-response rate of 10%, using a simple random sampling technique. In our study, the sample size determination was based on the assumption of the two-sided significance level of a 95%, power of 80%, control to case ratio of 3 to 1, taking a proportion of hypertension among the controls to be 19.6% (inferred from the population-based study) and with the assumption of the proportion to be double among the cases (39.2%). The study included all cases sequentially, and the next five consecutive non-cases for each case were included (which were age and gender-matched).

Despite the above difference, we learned a lot from their study and tried to improve some aspects of our association study. Notably, we decided to match the participants for important demographic characteristics and to omit clinical characteristics that had pathobiological or effect-modifying relation with a severe manifestation of a disease (in our case we omitted such potential modifiers after checking for bivariate collerate and multicollinear effect).

In our study, the association assessment was focused on a specific factor or variable mainly (hypertension) as an entry with patients grouped as severe and non-severe, whereas the Leulseged et al. 2022 tried to show association assessment with several factors across the severity spectrum of COVID-19 (mild, moderate, severe) separately in addition to the difference in the study population, sample size determination, and sampling technique.

- 2)The key problem with this study is that in the complex phenotype field, few researchers would have confidence in an association that is based on these small sample sizes. (Even if the authors stated as the power of the study).

Response: We agreed with the reviewer and here we tried to match the two study arms with important moderators(discharge date, age, and gender) of the outcome. But still, it will be complex if we consider matching for comorbidity or substance use, or others. For the novelty of the evidence to be generated, we opted for a 1:3 ratio case/control to improve the power of the study with strict sampling techniques.

- 3)The discussion could be made much more interesting. As it is, they primarily reiterate their results and provide a bit more literature review. However, it would be interesting if they could discuss clinical implications and areas for further study.

Response: This is an important comment and we incorporated pathological features and clinical implications with areas for further study in the Discussion section.

In paragraph 7 of the Discussion section:

The explanation for the higher prevalence of hypertension, diabetes mellitus, and cardiac disease among COVID-19 patients may focus on the SARS-CoV-2 cell entry mechanism. Similar to SARS-CoV-1, SARS-CoV-2 contains a receptor-binding domain (RBD) that recognizes angiotensin-converting enzyme 2 (ACE2) as its receptor with a higher binding affinity compared to SARS-CoV-1 [32]. Epithelial cells of the lungs, intestine, kidney, and blood vessels are identified to have abundant ACE2 receptors [33]. Hence, increased expression of ACE2 may promote the internalization of SARS-CoV-2, which in turn may increase the chances of developing COVID-19 or a severe form of the disease[34]. The severity of COVID-19 among patients with hypertension, diabetes, and chronic cardiac disease also may be partially explained by the increased incidence of thrombotic complications which is a fact that patients with these conditions are at increased risk of thrombotic events [35,36]. These chronic medical conditions often present with inflammation and weakened innate immune responses in affected individuals. This may predispose those individuals to infections and disease complications [37]. The high prevalence of fatal cases among COVID-19 patients with hypertension, diabetes, and chronic cardiac disease as comorbidity could be due to the induction of cytokine storm. Cytokine storms resulting in hyper-inflammation are the hallmarks of severe SARS-CoV-2 infection [38]. Metabolic inflammation as a consequence of hypertension, diabetes, and chronic cardiac disease is also known to compromise the immune system. These patients are commonly reported to have weakened immunological function arising from reduced macrophage and lymphocyte activity which could predispose individuals to infections, especially those infections for which cell-mediated immunity constitutes an important host defense [39].

Submitted filename: Response to Reviewers and Editor.docx

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12 May 2022

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Academic Editor

PLOS ONE

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Please address to the concerns raised by Reviewer 1. In-depth data analysis and presentation is necessary.

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Reviewer #1: This manuscript entitled "Assessment of hypertension and other factors associated with the severity of disease

in COVID-19 pneumonia" has been thoroughly assessed based on the overall weakness and strength of the manuscript. The manuscript hold scientific scope and can contribute in the unveiling pathogenesis of COVID19. However, after in depth analysis of manuscript a few significant inferences were noted.

1. The results appear to be too preliminary and disjointed for publication.

2. The authors have not enriched the manuscript significantly following the previous peer reviewed comments.

3. The authors should work on data presentation and in-depth analysis of data alongside expansion of the cohort size to meet the publication quality of the journal.

Abiding following points i would urge the editorial committee not to further consider this manuscript for publication in present format.

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24 Jun 2022

PLOS ONE

June 22, 2022

Dear Editor,

We greatly appreciate the comments of the reviewers of our manuscript and have addressed them here, point by point, and revised our manuscript accordingly.

Reviewer #1: Work on data presentation and in-depth analysis of data alongside an expansion of the cohort size to meet the publication quality of the journal

Response: Thank you for the comments and concerns raised to perform deep analysis using Cox proportion hazard (CoH). Here, I will try to kindly respond to why we couldn’t conduct the analysis further. As you may recall, our study design was a case-control where recruitment of study subjects was based on the severity of disease (COVID-19) status. Cases were those with severe forms of the disease including critical, while controls were those who had mild to moderate disease, including asymptomatic ones. Some of the cases were recruited when they came to the hospital in a severe or critical state, while the rest were recruited after they developed severe disease. The exposure was hypertension whereas other related factors were considered possible confounders to suppress the effect of the main exposure(hypertension). Most importantly, from the nature of our retrospective data, the time between the onset of the disease and the change in severity course is difficult to retrieve and estimate. Thus, I respectfully would like to notify you that the design of our study will not allow us to use the CoH.

Concerning the sample size, we edited the sentence under the strength and limitation part, under the discussion section, where we tried to clarify for you the points we raised about the disparity between the initial calculated sample size (252, composed of 63 cases and 189 controls) and the actual number of patients (265, composed of 75 cases and 190 controls) with majority matched 1 to 3. So, here we acknowledge the limitation we faced due to the strict matching criteria of the design, and we were short of controls matching to cases for age bands, sex, and discharge date criteria though we had an extra number of cases (75 vs 63).

In the paragraph on Strength and limitation part of the Discussion section

However, this study had a few limitations. First, the strict matching criteria, including the date of discharge on selecting one case for three controls, failed to fulfill the planned case-to-control ratio, we collected data for 75 cases for which we were supposed to collect proportionally 225 controls which makes the total sample size to be 300. However, we were able to retrieve data of 75 cases for 190 controls which made the total sample size 265, which is a bit higher than the initial calculated sample size (252, 63 cases for 189 controls) with a slightly higher number of those on case arm (75 vs 63).

Thank you for considering our research article. We hope that our revisions meet with your approval.

With best regards,

Submitted filename: Response letter 2 to PLOS ONE.docx

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1 Aug 2022

Assessment of hypertension and other factors associated with the severity of disease in COVID-19 pneumonia, Addis Ababa, Ethiopia: A case-control study

PONE-D-22-04541R2

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Kind regards,

Kanhaiya Singh, Ph.D

Academic Editor

PLOS ONE

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Reviewers' comments:

5 Aug 2022

PONE-D-22-04541R2

Assessment of hypertension and other factors associated with the severity of disease in COVID-19 pneumonia, Addis Ababa, Ethiopia: A case-control study

Dear Dr. Ashamo:

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