Tuberculosis and isoniazid prophylaxis among adult HIV positive patients on ART in Northwest Ethiopia.

BACKGROUND: Although antiretroviral therapy (ART) can avert tuberculosis (TB) incidence among human immunodeficiency virus (HIV) infected patients, the concomitant use of ART with isoniazid (INH) has a paramount effect. Despite this evidence, there is a paucity of data regarding TB incidence among HIV patients on ART with and without isoniazid prophylaxis and its predictors. Thus, this study sought to assess the incidence and predictors of TB among adult HIV positive patients on ART.
METHODS: This was a hospital based retrospective study including 368 adult HIV positive patients on ART in Gondar comprehensive specialized hospital between January 1, 2016, and April 30, 2019. Data was extracted from clinical laboratory and HIV care ART follow up clinic. The bi-variable and multivariable regression models were used to ascertain predictors of incident TB. Data was analyzed using SPSS version 20 software.
RESULTS: A total of 335 adult HIV positive patients were included in the analysis, of whom, 56 (16.7%) were developed incident TB. Being ambulatory and bedridden (AOR: 2.2, 95% CI: 1.1, 4.6), advanced WHO clinical HIV disease stage (III and IV) (AOR: 3.2, 95% CI: 1.6, 6.1), not taking INH (AOR: 2.8, 95% CI: 1.3, 5.9), and baseline CD4+ T cell count ≤ 200 cell/mm3 (AOR: 3.6, 95% CI: 1.8, 7.2) were found to be the predictors of tuberculosis incidence.
CONCLUSION: The study indicated a high TB incidence among HIV positive patients in Gondar. Therefore, scaling up the isoniazid preventive therapy program and its strict compliance is necessary to avert HIV fueled tuberculosis in HIV endemic areas.

Background

Globally, TB remained one of the main problems of health to mankind, especially in developing countries of sub-Saharan Africa, and is resurging again after the emergence of HIV pandemic [1]. Epidemiological studies indicated that HIV is a trigger for TB incidence, and people living with HIV (PLWH) have 20 times higher risk of developing TB related to those without HIV comorbidity [2]. This is partly due to HIV causes downregulation of the immune system directly by killing the host CD4+ T cells [3].

Antiretroviral therapy has a significant effect in averting TB incidence in PLWH. However, HIV infected patients taking ART remained susceptible to TB, and TB is still the leading cause of mortality among HIV positive patients taking ART [4, 5]. As a result, world health organization (WHO) recommended isoniazid preventive therapy (IPT) to avert the development of TB among PLWH besides prompt ART initiation [4]. Recently established studies indicated that the concomitant use of IPT with ART have synergetic effect in preventing TB among HIV infected patients. Despite this promising evidence, its implementation in the targeted group is compromised due to different reasons [5].

The government of Ethiopia planned to reduce TB related mortality by 90% and incident TB by 80% in 2030 compared to 2015 levels [2]. To assess this ambitious plan, an updated evidence related to TB incidence and associated factors including isoniazid (INH) prophylaxis intervention measures has immense importance. Therefore, this retrospective study explored TB incidence and its predictors among HIV positive adults at University of Gondar comprehensive specialized hospital. The results gained from this study will have a positive effect in IPT implementation, inform policy makers and program developers working at different levels of TB controlling measures, and also health care experts working in TB control and prevention measures.

Methods

Study area, design, and period

A retrospective study was conducted in University of Gondar comprehensive specialized hospital (UoGCSH), from February to June 2019. The UoGCSH is one of the pioneer teaching hospitals in Ethiopia, and is located in Amhara region, Northwest Ethiopia. The hospital has eight different laboratory sections, including ART laboratory for CD4+ T cell and viral load counts, which provides diagnostic, teaching, and research services for the university community, Gondar town inhabitants, and the nearby Woreda people at large.

Study participants and eligibility

All adult HIV positive patients aged from 18 to 60 years who were newly starting ART at UoGCSH ART clinic and who had at least one follow up within 6 to 12 months from January 1, 2016 to June 1, 2019 were included in this study. However, all children aged under 18 and senior citizens aged above 60 were not included as their immunity to infection is altered, and hence it may have effect on baseline CD4+ T cell counts that may lead to wrong interpretation of the result. Similarly, those adults diagnosed as having TB at baseline during ART initiation and patients with incomplete baseline data for important variables such as functional status, WHO clinical stage, CD4+ T cell count levels, and isoniazid prophylaxis status were excluded from the study.

Sample size determination and sampling procedures

The sample size was calculated by using single population proportion formula through EPI INFO version 7.2.2.6 with the assumption of 95% level of confidence, 5% marginal error, and by taking 16.58% TB incidence among adult HIV positive patients from previous study in Ethiopia (Geremew et al., 2020) [1]. Given these assumptions, the sample size was estimated to be 217. Moreover, considering 10% expected incomplete data record the final sample size was 245. Nevertheless, to increase the power of the study we recruited a total of 368 study participants who didn’t have baseline TB in this study. The records of all adult HIV positive patients initiating ART without baseline TB comorbidity and recorded from January 1, 2016 to June 1, 2019 were sorted from the electronic database to select the study participants. Thereafter, 368 study participants were selected using a simple random sampling technique through computer generated numbers.

Data collection tool and procedures

Data abstraction tool was prepared from ART monitoring and evaluation forms. After preparing the extraction tool, consistency and completeness of the tool was verified compared to data recording systems by randomly selecting and completing a few chart reviews. Thereafter, minor amendments of the data collection tool were made accordingly before the beginning of data collection to ensure data quality. The tool includes sociodemographic, baseline clinical and INH prophylaxis associated variables. Data collectors were trained regarding each description of the tool and the way they collect data from patient charts. In order to pick charts from patient chart room, a medical record unique identifier number was first taken from the electronic record. Then, data was collected from the patient’s medical charts using prepared data abstraction tool. A commonly agreed code by data collectors was used to avoid unintentional recollection of data. All selected patient charts fulfilling the eligibility criteria were reviewed and data abstraction was completed in this way.

Measurements

The development of new TB within 12 months after ART initiation regardless of the time event was the dependent variable. Whereas the predictor variables were; sociodemographic characteristics (age, sex, and employment status), baseline clinical and laboratory characteristics (functional status, WHO clinical stage, and CD4+ T cell counts), and other medications (isoniazid prophylaxis). This study mainly focuses on the number of new TB cases within a year rather than the time to new TB development for HIV positive adults after ART initiation till the end of the study. For this study, incidence of TB is defined as the occurrence of TB cases which is confirmed by bacteriological testes (at least one positive AFB microscopy, culture positive, Xpert MTB/Rif assay positive) or based on clinical decision of expert physician after initiation of ART during follow up [6].

Data analysis

Data were entered into epidata and exported to statistical package for the social sciences (SPSS) version 20 software. Frequencies and percentages were used to summarize characteristics of study participants. Bivariate logistic regression analysis was performed to determine the association of each individual independent variable with the outcome variable. As a result, crude odds ratio (COR) with corresponding 95% confidence intervals (95% CI) was obtained. Multiple logistic regression analysis was performed to assess simultaneously the association between multiple risk factors and the log odds of being positive for TB incidence. From this model, adjusted odds ratios (AOR) and 95% CI were obtained and then variables with P value <0.05 were considered as statically significant.

Ethical considerations

Ethical clearance was obtained from the Institutional Review Board (IRB) of the University of Gondar, School of Biomedical and Laboratory Sciences. The IRB waived the requirement for informed consent to collect and retrieve data from the patients’ medical chart. In addition, confidentiality was maintained during data extraction by using only unique identification codes rather than patient names.

Results

Baseline sociodemographic and clinical profiles of study participants

After exclusion of thirty-three (33) charts due to data incompleteness, 335 adult HIV positive patients’ records were included based on the predefined inclusion criteria and considered in the final analysis.

From 335 participants included in the analysis, about 182 (54.3%) were females. The mean age of the study participants were 36.7 years with a standard deviation (SD) of 9.2 years, and 176 (52.5%) of the total subjects were in the age group of 31 to 45 years. The majority of the patients 201 (60%) were unemployed, 276 (82.4%) had working functional status, 215 (64.2%) had WHO clinical stage I and II, 119 (35.5%) had isoniazid prophylaxis, while 246 (73.4%) of the participants had CD4+ T cell counts > 200 cell/mm3 (Table 1).

Table 1

Baseline demographic and clinical profiles of study participants living with HIV in Gondar.

Variables	Frequency (n)	Percentage (%)
Age
19–30	105	31.3
31–45	176	52.5
46–65	54	16.2
Sex
Male	153	45.7
Female	182	54.3
Employment status
Employed	134	40.0
Unemployed	201	60.0
Functional status
Working	276	82.4
Ambulatory-bedridden	59	17.6
WHO stage
I/II	215	64.2
III/IV	120	35.8
INH prophylaxis
Yes	119	35.5
No	216	64.5
CD4+ T cell count
> 200 cell/mm3	246	73.4
≤ 200 cell/mm3	89	26.6

Tuberculosis incidence

The incidence of tuberculosis at the end of 12 months of follow up after ART initiation was 56/335 (16.7%). More specifically, TB incidence with and without INH prophylaxis was 8.4% and 21.3%, respectively. The incidence of TB among men and women were 27 (17.6%) and 29 (15.9%), correspondingly. Regarding WHO clinical HIV disease stage, the incidence of TB on HIV infected adults on stage I/II were 11.2% while among HIV patient who were on advanced disease stage (III or IV) the incidence was 26.7% (Table 2).

Table 2

TB incidence with different baseline demographic and clinical profiles of study participants living with HIV in Gondar.

Variables	Total patients, (n = 335)	TB incidence
		Yes, n (%)	No, n (%)
Total patients, n (%)	335 (100)	56 (16.7%)	279 (83.3)
Age years, Mean ± SD	36.7 ± 9.2	38.2 (8.7)	36.4 (9.3)
Sex, n (%)
Male	153 (45.7)	27 (17.6)	126 (82.4)
Female	182 (54.3)	29 (15.9)	153 (84.1)
Employment status, n (%)
Employed	134 (40.0)	23 (17.2)	111 (82.8)
Unemployed	201 (60.0)	33 (16.4)	168 (83.6)
Functional status, n (%)
Working	276 (82.4)	39 (14.1)	237 (85.9)
Ambulatory-bedridden	59 (17.6)	17 (28.8)	42 (71.2)
WHO stage, n (%)
I/II	215 (64.2)	24 (11.2)	191 (88.8)
III/IV	120 (35.8)	32 (26.7)	88 (73.3)
INH prophylaxis, n (%)
Yes	119 (35.5)	10 (8.4)	109 (91.6)
No	216 (64.5)	46 (21.3)	170 (78.7)
CD4+ T cell count, n (%)
> 200 cell/mm3	246 (73.4)	32 (13.0)	214 (87.0)
≤ 200 cell/mm3	89 (26.6)	24 (27.0)	65 (73.0)

NB: SD = Standard Deviation INH = Isoniazid.

Factors associated with incidence of TB among HIV infected adults

After adjusting the potential confounder using multivariant regression, variables including being ambulatory and bedridden functional status (AOR: 2.2, 95% CI: 1.1, 4.6), having advanced HIV disease stage III/IV (AOR: 3.2, 95% CI: 1.6, 6.1), not taking INH prophylaxis (AOR: 2.8, 95% CI:1.3, 5.9), and having low baseline CD4+ T cell count (AOR: 3.6, 95% CI:1.8, 7.2) remained significantly associated with TB incidence among HIV infected adults (Table 3).

Table 3

Predictors of TB incidence in adults living with HIV in Gondar.

Variables	TB incidence		COR (95%CI)	AOR (95%CI)
	Yes, n (%)	No, n (%)
Age groups
19–30	14 (25.0)	91 (32.6)	1	1
31–45	34 (60.7)	142 (50.9)	1.5 (0.7, 3.1)	1.6 (0.8, 3.5)
46–65	8 (14.3)	46 (16.5)	1.1 (0.4, 2.9)	1.3 (0.5, 3.9)
Sex
Male	27 (48.2)	126 (45.2)	1	1
Female	29 (51.8)	153 (54.8)	0.8 (0.5, 1.6)	1.1 (0.6, 2.1)
Employment status
Employed	23 (41.1)	111 (39.8)	1	1
Unemployed	33 (58.9)	168 (60.2)	0.9 (0.5, 1.7)	0.9 (0.5, 1.7)
Functional status
Working	39 (69.6)	237 (84.9)	1	1
Ambulatory-bedridden	17 (30.4)	42 (15.1)	2.3 (1.2, 4.4)	2.2 (1.1, 4.6)
WHO stage
I/II	24 (42.9)	191 (68.5)	1	1
III/IV	32 (57.1)	88 (31.5)	2.9 (1.6, 5.2)	3.2 (1.6, 6.1)
INH prophylaxis
Yes	10 (17.9)	109 (39.1)	1	1
No	46 (82.1)	170 (60.9)	2.9 (1.4, 6.1)	2.8 (1.3, 5.9)
CD4+ T cell count
> 200 cell/mm3	32 (57.1)	214 (76.7)	1	1
≤ 200 cell/mm3	24 (42.9)	65 (23.3)	2.5 (1.4, 4. 5)	3.6 (1.8, 7.2)

NB: COR: Crud Odd Ratio, AOR: Adjusted odd ratio. Bold numerals indicated that significantly associated with dependent variables.

Discussion

Tuberculosis remains one of the leading causes of morbidity, and is responsible for one third of death among people living with HIV globally, especially in developing countries including Ethiopia [7-9].

In this study, the overall incidence of TB among ART initiated HIV positive adults was 16.7% (95% CI: 13, 21%) at the end of the follow up period. This is in line with study conducted in Debre Markos referral hospital, Northwest Ethiopia reported as 16.9% [2], in Shegaw Motta district hospital, Ethiopia 18% [10], in Hawassa University referral hospital, Southern Ethiopia 18.2% [11] and the finding in India 17% [12].

However, TB incidence rate revealed in this study is higher than previously established evidences in different regions of the country; 7.5% of TB prevalence in Gondar university hospital, Northwest Ethiopia [13], 10.3% overall pooled TB incidence in Ethiopia [5], 12.7% in Addis Ababa, Ethiopia [14], 7.2% in Arba Minch general hospital, Southern Ethiopia [15], 11.4% in Dessie referral hospital [16], 12.6% in Debre Markos referral hospital, Ethiopia [17] and 11% TB prevalence rate reported from Northwestern Tanzania [18]. This is probably attributed to the variation in sample size and/or in the duration of the follow up time. Partly, this could be because of the difference in TB case management and the use of tools to implementing the end TB strategy in different settings [19].

This study also revealed that HIV positive patients with bedridden and/or ambulatory functional status at enrolment were having 2.2 times higher risk of developing TB compared to their counterparts, working individuals (AOR: 2.2, 95% CI: 1.1, 4.6). This is similar with other previous studies conducted by Belew et al., [20], Temesgen et al., [2] and Alemu et al., [14]. This might be due to bedridden or ambulatory HIV positive patients were unable to perform their day to day activities, as a result there might be a downregulated immune functions including a decrease in their CD4+ T cell counts and make them more susceptible to different viral and bacterial infections including TB [21, 22].

Advanced clinical WHO disease stage was another important independent predictor of TB incidence among HIV infected adults on ART in this study. Accordingly, the odds of developing TB was 3.2 times more likely for study participants with HIV disease stage III or IV as compared to patients on clinical early disease stage I and II (AOR: 3.2, 95% CI: 1.6, 6.1). This finding is in accordance with different earlier studies conducted nationally [2, 14, 23] and internationally [24]. This is partly due to patients with advanced clinical stage might be highly immunocompromised and subsequently leads to the recurrence of those low virulence opportunistic pathogens including TB infection [25]. However, a study conducted in Nigeria showed that there is no significant association between WHO clinical HIV stage with the incidence of TB among HIV infected people on ART [26].

In addition, this study demonstrated that taking INH prophylaxis was the significant independent predictors of TB among HIV infected adults on ART. Subsequently, study subjects who didn’t took INH prophylaxis were having 2.8 times more risk of getting TB than those who took INH (AOR: 2.8, 95% CI:1.3, 5.9). This finding was consistent with earlier studies conducted in different study areas [17, 18, 27], suggesting that taking INH prophylaxis is the preventive factor for TB occurrence. This is partly due to the concomitant use of INH with ART have synergetic effect in preventing TB incidence among HIV infected patients [5] by improving the quantity and functional aspects of immunological markers including CD4+ T cell counts.

Lastly, this study also showed that lower baseline CD4+ T cell counts (≤ 200 cell/mm3) were another important determinant factor of TB incidence among HIV infected adults. Consequently, participants with baseline CD4+ T cell counts ≤ 200 cell/mm3 had 3.6 times increased risk of developing TB as compared to individuals who had CD4+ T cell counts > 200 cell/mm3. This finding is consistent with previous studies conducted in different parts of Ethiopia including Southern Ethiopia [28], Jimma, Ethiopia [23], and in another parts of the world such as Nigeria [26], India [12] and Tanzania [24]. This is partly because of low CD4+ T cell counts in HIV infected patients indicates severe immunosuppression which makes the patients more susceptible to new or recurrent TB infection. Meanwhile, this finding is not consistent with other earlier finding where CD4+ T cell counts was not significant predictors of TB among HIV infected patients receiving ART [29].

Limitation of the study

The main limitation of this study was unable to detected virological failure which is the principal and direct indicators of immune status of the patients. The other limitation of the study was retrospective nature of the study design.

Conclusion and recommendation

In this study, incidence of TB among HIV infected adults was significantly high. Adult patients on advanced HIV disease (stage III/IV), being ambulatory functional status, not taking INH and low baseline CD4+ T cell counts were more likely to develop TB. Therefore, early detection and treatment of opportunistic infection should give a special attention. Furthermore, scaling up the INH prophylaxis program and its strict compliance is necessary to avert HIV fueled tuberculosis in the area.

(SAV)

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9 Feb 2022

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Although the manuscript is fairly well written, I agree with the reviewers that study design is not robust and specially the objectives of the study. The issue regarding model of the study is raised by both reviewers and therefore, author need to demonstrate the aim of the study with pretested instrument.

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Reviewer #1: I must congratulate authors for writing on this important topic beautifully. I've only two issues related to the manuscript.

1. The Tuberculosis incidence definition is not mentioned in the manuscript. How the tuberculosis diagnosis was done? Is it a routine process that the cases of HIV (PLHIV) at the time of HIV diagnosis are screened for tuberculosis?

2. Since the study has not tested the relation between the ART and tuberculosis, the statement "In this study, incidence TB among HIV infected adults on ART were significantly high." is not applicable as a concluding statement.

Reviewer #2: Authors have attempted to describe the incidences of TB among HIV and further the strength of association with predictors .Although this is nearer to retrospective/chart review which is sometimes consider the major concern .In my humble opinion it may be overcome (and should not be a major concern) if investigators have strong theoretical construct before commencing the study .This does not seem the case in this study. The analysis is driven by the data and not by the theory which makes the inferences fragile , incidental and highly corelated to each other. For example WHO staging and functional status are highly corelated intuitively and clinically . Keeping these 2 variables simultaneously may not assign any predictive power to the model .

Moreover the model diagnostics ( R-square, -2LL ) are not shown by the authors .It is importance to understand the ratio of explained variance to unexplained variance (noise ) by the model . They are requested to prepare competitive models in increasing complexity before directly proceeding for data analysis by intuitively and logically selecting the variables and then they should select the most parsimonious yet on with explaining the maximum variance in the data set .

Another point which I would request to authors to think outcome -measurement as dynamic phenomenon and not as a static one. As of now they have taken the outcome measurement regardless of time event which actually beats the fundamental purpose of cohort study . They may apply the cox proportion regression hazard model as to understand the differential probability (odds) of developing tuberculosis at different point of time .This finding may give an indication to clinical vigilance by treating physician.

There are some syntax error in the sentence formations in data analysis section ( page-12 /2nd line) and result section (page-13/2nd para) which may be rewritten by authors for clarity purpose.

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Reviewer #2: Yes: Ankur Joshi

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8 Mar 2022

Authors’ response letter, Manuscript ID - PONE-D-21-18222

Thank you, the editorials, and reviewers for your valuable time and effort to share your experience and review our manuscript in detail. We the authors have addressed all comments and suggestions forwarded from the editors and reviewers. Our point-by-point detailed scientific justification and technical improvements follows the reviewer’s comments, and all page numbers refers to the cleaned revised manuscript file.

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2. Thank you for including your ethics statement: "Ethical clearance was obtained from the Institutional Review Board (IRB) of the University of Gondar, School of Biomedical and Laboratory Sciences. Besides, informed consent was obtained from the school and ART focal person to collect and retrieve the data from the patients’ chart. In addition, confidentiality was maintained during data extraction by using only unique identification codes rather than patient names.

a) Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please ensure that you have specified (1) whether consent was informed and (2) what type you obtained (for instance, written or verbal, and if verbal, how it was documented and witnessed). If your study included minors, state whether you obtained consent from parents or guardians. If the need for consent was waived by the ethics committee, please include this information.

If you are reporting a retrospective study of medical records or archived samples, please ensure that you have discussed whether all data were fully anonymized before you accessed them and/or whether the IRB or ethics committee waived the requirement for informed consent. If patients provided informed written consent to have data from their medical records used in research, please include this information.

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Authors’ response: Thank you for critically looking at the ethical issue. As this study was retrospective in nature and the data were accessed by reviewing medical records without direct contact of study participants, the school of biomedical and laboratory science, University of Gondar IRB waived the requirement for any informed consent.

3. Thank you for stating the following financial disclosure:

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Authors’ response: Thank you the editors again for your suggestion. Regarding to funding, we addressed it in the revised manuscript (bottom of page 14) by saying “The authors received no specific funding for this work.”

Additional Editor Comments:

Although the manuscript is fairly well written, I agree with the reviewers that study design is not robust and specially the objectives of the study. The issue regarding model of the study is raised by both reviewers and therefore, author need to demonstrate the aim of the study with pretested instrument.

Authors’ response: Thank you the editors for your appreciation. Hence the main objectives of the study was to determine the incidence of TB among HIV infected patients under ART and the outcome variable was dichotomous in nature , we use both bivariable and multivariable logistic regression model and all the goodness of model fitness was assessed by Hosmer-Lemeshow Test due to that the sample size was satisfactory.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

Authors’ response: Thank you all the reviewers. The three years data collected from 2016-2019 indicated that the incidence of tuberculosis among adult HIV infected participants on ART was (16.7%) and more specifically, TB incidence with and without INH prophylaxis was 8.4% and 21.3%, respectively. Based on this data we concluded that the incidence of TB was high in the study area. This means that the data can support the conclusion and it is very informative indication for policymakers.

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Authors’ response: We are thankful to all reviewers for your great appreciation. To ensure the strength of the association of explanatory variables with the outcome variables, we perform bivariant and multivariant logistic regression which is relevant for the objective of this study.

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Authors’ response: Thank you for your appreciation.

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Authors’ response: Thank you once again for your encouragement.

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Comments from reviewer 1

I must congratulate authors for writing on this important topic beautifully. I've only two issues related to the manuscript.

1. The Tuberculosis incidence definition is not mentioned in the manuscript. How the tuberculosis diagnosis was done? Is it a routine process that the cases of HIV (PLHIV) at the time of HIV diagnosis are screened for tuberculosis?

Authors’ response: This is a very interesting comment and we the authors also strongly agree with your insight. The definition of TB incidence was defined in the revised document (bottom of page 6, last sentence of under the heading “measurement”).

2. Since the study has not tested the relation between the ART and tuberculosis, the statement "In this study, incidence TB among HIV infected adults on ART were significantly high." is not applicable as a concluding statement.

Authors’ response: Great thanks for your constructive comments. Yes, you are correct that, we didn’t assess the association between ART and TB in this study even if the study participants were on ART. Then, as per the reviewer comments, we carefully revised the conclusion parts of the document. Please you may check the revised manuscript once again.

Comments from reviewer 2

Authors have attempted to describe the incidences of TB among HIV and further the strength of association with predictors. Although this is nearer to retrospective/chart review which is sometimes consider the major concern. In my humble opinion it may be overcome (and should not be a major concern) if investigators have strong theoretical construct before commencing the study. This does not seem the case in this study. The analysis is driven by the data and not by the theory which makes the inferences fragile, incidental and highly corelated to each other. For example, WHO staging and functional status are highly corelated intuitively and clinically. Keeping these 2 variables simultaneously may not assign any predictive power to the model.

Authors’ response: Thank you the reviewer for your great ideas. Before commencing the data collection, we have looked for the theoretical aspects of the association of TB incidence on HIV-infected individuals. The mechanisms of TB infection among HIV-infected individuals were discussed in detail. Furthermore, we rule out the major explanatory variables of incidence of TB like HIV disease stage and their functional status of the patients after reviewing recently published literature around the globe. We strongly agree with you that in the case of the advanced disease stage the patient becomes hospitalized which indicates that they may correlate with each other. In order to remove potential confounders like those, we analyse multiple logistic regression after doing bivariable logistic regression as the type of data was dichotomies.

Moreover, the model diagnostics (R-square, -2LL) are not shown by the authors. It is importance to understand the ratio of explained variance to unexplained variance (noise) by the model. They are requested to prepare competitive models in increasing complexity before directly proceeding for data analysis by intuitively and logically selecting the variables and then they should select the most parsimonious yet on with explaining the maximum variance in the data set.

Authors’ response: Great thanks for sharing your statistical experience that was untouched by the authors. However, in the current study “Hosmer and Lemeshow” analysis was performed for assessing model fitness as the sample size was high instead of using the -2 loglikelihood or -2LL. Additionally, the likelihood ratio test does not always perform well, especially when data are sparse. R-Squared is a statistical measure of fit that indicates how much variation of a dependent variable is explained by the independent variables in a regression model. However, this type of model is applied for linear regression where the data type of dependent and independent was continuous variable which is distinctively different from our data type. So please consider as the current data type is dichotomous which didn’t fulfil the linear regression assumption criteria.

Another point which I would request to authors to think outcome -measurement as dynamic phenomenon and not as a static one. As of now they have taken the outcome measurement regardless of time event which actually beats the fundamental purpose of cohort study. They may apply the cox proportion regression hazard model as to understand the differential probability (odds) of developing tuberculosis at different point of time. This finding may give an indication to clinical vigilance by treating physician.

Authors’ response: Thank you for your detailed reviewing the analysis part of the document and strong supporting idea. In this study we didn’t apply Cox proportional hazards models because these models are usually applied to prospective studies that have a follow-up period during which the occurrence of events is observed. Whereas our study mainly focuses on the number of new TB cases within a year rather than the time to new TB development for HIV positive adults after ART initiation and we haven’t any follow-up data then logistic regression models were applied for this cross-sectional study.

There are some syntax error in the sentence formations in data analysis section ( page-12 /2nd line) and result section (page-13/2nd para) which may be rewritten by authors for clarity purpose.

Authors’ response: Many thanks to the reviewer for this positive feedback, which we appreciate. We have now revised all unclear sentences in the data analysis and result section to ensure the sentences are clear and understandable to the PLOS One ID audience. Please see over the revised manuscript once again.

Submitted filename: Response to Reviewers.docx

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29 Mar 2022

Tuberculosis and isoniazid prophylaxis among adult HIV positive patients on ART in Northwest Ethiopia.

PONE-D-21-18222R1

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13 Apr 2022

PONE-D-21-18222R1

Tuberculosis and isoniazid prophylaxis among adult HIV positive patients on ART in Northwest Ethiopia.

Dear Dr. Geremew :

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