Predictive utility of the C-reactive protein to albumin ratio in early allograft dysfunction in living donor liver transplantation: A retrospective observational cohort study.

BACKGROUND: This study was performed to determine the association between the ratio of C-reactive protein to albumin (CRP/ALB) and the risk of early allograft dysfunction (EAD) in patients undergoing living donor liver transplantation (LDLT). PATIENTS AND METHODS: A total of 588 adult patients undergoing LDLT were retrospectively investigated, after 22 were excluded because of signs of overt infection or history of ALB infusion. The study population was classified into high and low CRP/ALB ratio groups according to EAD. All laboratory variables, including CRP and ALB, had been collected on the day before surgery. A percentage value for the CRP/ALB ratio (%) was calculated as CRP/ALB × 100.
RESULTS: After LDLT, 83 patients (14.1%) suffered EAD occurrence. A higher CRP/ALB ratio was independently associated with risk of EAD, Model for End-stage Liver Disease score, fresh frozen plasma transfusion, and donor age. Based on a cutoff CRP/ALB ratio (i.e., > 20%), the probability of EAD was significantly (2-fold) higher in the high versus low CRP/ALB group. The predictive utility of CRP/ALB ratio for EAD was greater than those of other inflammatory markers. In addition, patients with a high CRP/ALB ratio had poorer survival than those with a low CRP/ALB ratio during the follow-up period.
CONCLUSIONS: The easily calculated CRP/ALB ratio may allow estimation of the risk of EAD after LDLT and can provide additional information that may facilitate the estimation of a patient's overall condition.

Introduction

Living donor liver transplantation (LDLT) has been widely accepted as one of the definitive treatments for patients with end-stage liver disease (ESLD) [1]. The patient and graft survival rates of LDLT and deceased donor liver transplantation (DDLT) are comparable [2]. However, because partial liver grafts are transplanted in LDLT, which requires concomitant liver regeneration and functional recovery, the possibility of postoperative graft dysfunction, referred to as “small-for-size syndrome,” remains [3,4]. In patients with ESLD who are scheduled for liver transplantation (LT), many factors may influence the occurrence of early allograft dysfunction (EAD) after LT, such as kidney disease, renal replacement therapy, the Model for End-Stage Liver Disease (MELD) score, and donor characteristics [4-7]. Severe systemic inflammation before surgery has been shown to be related to patients’ increased risk of EAD development in the LDLT setting [8,9]. A previous LDLT study demonstrated significant associations of the neutrophil-to-lymphocyte ratio (NLR) with EAD, 1-year graft failure, and mortality following surgery [8]. As the occurrence of EAD seems to be related to severe inflammatory activity derived from ischemia–reperfusion injury [10,11], the preoperative immune condition in patients undergoing LDLT may be a useful predictor of the degree of ischemia–reperfusion injury, as supported by the relationship between the preoperative levels of proinflammatory biomarkers (i.e., interleukin [IL]-2, -6, and -17) and the occurrence of EAD [9,12]. Previous studies suggested that EAD is a reversible condition that can improve during the natural postoperative course [3,6]. Nevertheless, the risk of EAD development should be estimated in patients undergoing LDLT.

Accumulating evidence supports the clinical utility of the C-reactive protein to albumin (CRP/ALB) ratio for predicting morbidity and/or mortality in critically ill patients [13,14]. CRP is a valuable acute-phase inflammatory marker that is produced in response to infection, ischemia, and trauma, and is synthesized by hepatocytes, smooth muscle cells, macrophages, endothelial cells, lymphocytes, and adipocytes under regulation by proinflammatory cytokines, particularly interleukin-6 [15-23]. A lower ALB level is related to the severity of inflammation or malnutrition [24-26], and has been proposed as a clinical tool for the estimation of hepatic insufficiency [27]. CRP and ALB have been studied widely in various clinical settings and have been recognized as valuable prognostic markers for outcomes across various diseases, including sepsis, neoplasia, critical illness after intensive care unit (ICU) admission, and hospital-acquired acute kidney injury [28-32]. The CRP/ALB ratio, a combined index of the ALB and CRP levels, is known to be related more consistently to prognosis than is CRP or ALB alone, and it may accurately reflect the degree of inflammation or nutritional deficiency [13,14,33,34]. However, as the pathological mechanisms of ESLD (i.e., hepatic insufficiency and/or malnutrition) may negatively influence CRP and ALB production, cirrhotic patients have always been excluded from previous studies [13,14,25]. Therefore, no studies have determined the associations between CRP/ALB ratio and risks of poor graft outcomes, such as EAD, in patients undergoing LDLT.

This study was performed to examine the relationship between CRP/ALB ratio and risk of EAD development in patients undergoing LDLT. In addition, we compared the utility of CRP/ALB ratio with that of other inflammatory markers for the prediction of EAD development, and sought to determine the optimal CRP/ALB ratio cutoff for predicting EAD. Postoperative outcomes were compared between the non-EAD and EAD groups.

Patients and methods

Ethical considerations

The Institutional Review Board of Seoul St. Mary’s Hospital Ethics Committee approved the present study (KC19RESI0214) on April 15, 2019, and the study was performed in accordance with the principles of the Declaration of Helsinki. The requirement for informed consent was waived because of the retrospective nature of the study.

Study population

Data for 610 adult patients (aged > 19 years) who underwent elective LDLT between January 2009 and December 2018 at Seoul St. Mary’s Hospital were retrospectively collected from the electronic medical record system. The exclusion criteria included signs of overt preoperative infection (e.g., pneumonia or spontaneous bacterial peritonitis), with identification of the source of infection by culture from blood, urinary ascites, and/or sputum, chest X-ray or computed tomography (CT) of the lung and/or abdomen, or based on patients’ clinical presentation [35]; history of ALB infusion within 1 week before surgery (where this could artificially inflate or lower CRP/ALB ratio); and missing laboratory data. Ultimately, 588 adult patients were enrolled in this study.

Living donor liver transplantation

The surgical and anesthetic management protocol was described in detail previously [36]. Briefly, the piggyback surgical technique was applied in the right liver lobe with reconstruction of the middle hepatic vein. After the completion of hepatic vascular and ductal anastomoses (i.e., hepatic vein, portal vein, hepatic artery, and bile duct in a serial manner), the patency of the hepatic vascular flow (i.e., portal venous flow [PVF] and hepatic arterial resistive index [HARI]) was assessed using Doppler ultrasonography (Prosound SSD-5000; Hitachi Aloka Medical, Tokyo, Japan). Surgical inflow modification via splenectomy, splenic artery ligation, or a portocaval shunt was performed based on the discretion of the transplant surgeon.

Balanced anesthesia was performed based on hemodynamic measurements (i.e., mean blood pressure [MBP] ≥ 65 mmHg and central venous pressure [CVP] ≤ 10 mmHg). According to transfusion guidelines [37], packed red blood cells (PRBCs) were transfused to achieve a hematocrit ≥ 25%, and coagulation factors (i.e., fresh frozen plasma [FFP], single donor platelets [SDPs], and cryoprecipitate) were recovered with guidance of laboratory estimation or thromboelastography.

Nephrologists routinely assessed the kidney function of patients undergoing elective LDLT according to the estimated glomerular filtration rate (eGFR), derived using the Modification of Diet in Renal Disease formula: eGFR = 175 × standardized serum creatinine−1.154 × age−0.203 × 1.212 (if black) × 0.742 (if female) [38]. Based on the eGFR, the degree of kidney function was quantified as chronic kidney disease (CKD) stage 1 (i.e., normal function and eGFR ≥ 90 mL/min/1.73 m2), stage 2 (i.e., mild function loss and eGFR 60–89 mL/min/1.73 m2), stage 3a (i.e., mild to moderate function loss and eGFR 45–59 mL/min/1.73 m2), stage 3b (i.e., moderate to severe function loss and eGFR 30–44 mL/min/1.73 m2), stage 4 (i.e., severe function loss and eGFR 15–29 mL/min/1.73 m2), and stage 5 (i.e., kidney failure and eGFR < 15 mL/min/1.73 m2) [39]. Patients with severe preoperative loss of kidney function (i.e., CKD stage 5) were provided continuous renal replacement therapy (CRRT) before and during surgery [40,41].

Significant post-reperfusion syndrome (PRS) was defined as unstable and persistent vital signs (i.e., MBP ≥ 30% in the anhepatic phase or hypotensive duration ≥ 5 min), fatal arrhythmia (i.e., asystole or ventricular tachycardia), requirement for strong rescue vasopressors (i.e., epinephrine or norepinephrine infusion), continuing or reoccurring fibrinolysis, or a requirement for anti-fibrinolytic drug treatment [42].

An immunosuppressive regimen (calcineurin inhibitor, mycophenolate mofetil, or prednisolone) was administered according to our hospital LDLT protocol. Basiliximab was administered prior to surgery and on postoperative day (POD) 4. These immunosuppressants were gradually tapered after LDLT.

Early allograft dysfunction

EAD was clinically determined by the presence of more than one of the following: (1) bilirubin ≥ 10 mg/dL on POD 7; (2) international normalized ratio [INR] ≥ 1.6 on POD 7; and (3) alanine or aspartate aminotransferase > 2000 IU/mL on POD 7 [5,7].

The study population was divided into non-EAD and EAD groups.

Measurement of C-reactive protein and albumin

As part of the preoperative patient assessment, laboratory parameters, including CRP and ALB levels, were measured in all patients scheduled for LDLT. All laboratory data were collected via venous or arterial blood sampling (Clot Activator Tube/BD Vacutainer; Becton, Dickinson and Company, Franklin Lakes, NJ, USA) on the day before surgery and were measured using an automated chemistry analyzer (Hitachi 7600; Hitachi Ltd., Tokyo, Japan). If multiple tests were performed during 1 day, the results of the test performed nearest to surgery were used in the analysis, and laboratory parameters, such as CRP/ALB ratio and neutrophil to lymphocyte ratio (NLR), were derived from variables measured at the same time.

The ratio of CRP to ALB, as a percentage value, was calculated as CRP/ALB × 100 [13,14].

Perioperative recipient and donor-graft findings

Preoperative recipient data recorded within 7 days before surgery included age, sex, body mass index (BMI), etiology of LDLT, hepatocellular carcinoma (HCC), HCC beyond the Milan criteria [43], comorbidities (i.e., diabetes mellitus and hypertension), MELD score, eGFR-based kidney function grade, hepatic decompensation (i.e., encephalopathy [West Haven grade I or II] [44], varix, and ascites) status, transthoracic echocardiography findings (i.e., ejection fraction and diastolic dysfunction [45]), and laboratory variables (i.e., white blood cell [WBC] count, NLR, CRP/ALB ratio, CRP, ALB, platelet count, sodium, potassium, calcium, glucose, and ammonia).

Intraoperative recipient findings included duration of surgery, significant PRS, vital signs (i.e., MBP, heart rate [HR], and CVP), mean lactate, blood product transfusion (i.e., PRBCs, FFP, SDPs, and cryoprecipitate), hourly fluid infusion status, hourly urine output, and Doppler ultrasonography (i.e., HARI and PVF). Donor-graft findings included age, sex, BMI, graft-recipient weight ratio, graft ischemia time, and fatty change (%).

Postoperative outcomes included total duration of hospital stay, eGFR-based kidney function grade, ascites, infection (i.e., pneumonia or sepsis), graft rejection [46], occurrence of de novo cancer, incidence of re-transplantation due to graft failure, and overall patient mortality.

Statistical analysis

The perioperative recipient and donor-graft findings were compared between the non-EAD and EAD groups using the Mann–Whitney U test and the χ2 test or Fisher’s exact test, as appropriate. The predictive accuracy of the inflammatory markers, including CRP/ALB ratio, for EAD development were estimated using the area under the receiver operating characteristic curve (AUC). In addition, the optimal cutoff of the CRP/ALB ratio for the prediction of EAD development was determined using the AUC. The association between the perioperative factors and EAD was analyzed by univariate and multivariate logistic regression. Potentially significant factors (p < 0.1) in the univariate analysis were entered into multivariate forward and backward logistic analyses. When multiple perioperative variables were inter-correlated, the most clinically relevant factors were retained in the analyses. The predictive accuracy of the models was evaluated using the AUC. The values are expressed as medians (interquartile range [IQR]) and numbers (proportion). In all analyses, p < 0.05 was taken to indicate statistical significance. Statistical analyses were performed using SPSS for Windows (ver. 24.0; SPSS Inc., Chicago, IL, USA) and MedCalc for Windows software (ver. 11.0; MedCalc Software, Ostend, Belgium).

Results

Demographic characteristics of patients undergoing LDLT

The study population was predominantly male (70.2%) and the median (IQR) age and BMI were 53 (48–59) years and 24.2 (22.1–26.6) kg/m2, respectively. The most common etiologies of LDLT were as follows: hepatitis B (HBV) (54.1%), alcoholic hepatitis (23.0%), hepatitis C (6.6%), autoimmune hepatitis (4.6%), hepatitis A (4.1%), drug and toxic hepatitis (2.4%), and cryptogenic hepatitis (5.3%). The median (IQR) MELD score and CRP/ALB ratio were 15 (9–26) points and 13.9% (3.8%–54.2%), respectively. The incidence of EAD was 14.1% and the median (IQR) follow-up period was 3.6 (1.3–6.6) years.

Comparison of pre- and intraoperative recipient and donor-graft findings according to EAD development

As shown in Table 1, there were intergroup differences in preoperative recipient findings (i.e., age; prevalence of HCC and HCC beyond the Milan criteria; MELD score; eGFR-based kidney function grade; incidence of ascites; and laboratory values for WBC count, NLR, CRP/ALB ratio, CRP, ALB, sodium, and glucose). As shown in Table 2, there were also group differences in intraoperative recipient findings (i.e., incidence of postreperfusion syndrome; average HR; total PRBC, FFP, SDP, and cryoprecipitate transfusion amounts; and hourly urine output) and donor-graft findings (i.e., age and graft ischemic time).

Table 1

Preoperative recipient findings of the non-EAD and EAD groups.

Group	non-EAD	EAD	p
n	505	83
Age (years)	54 (49–60)	52 (46–55)	0.015
Sex (male)	356 (70.5%)	57 (68.7%)	0.737
Body mass index (kg/m2)			0.319
Underweight (<18.5)	13 (2.6%)	5 (6.0%)
Ideal weight (18.5–24.9)	283 (56.0%)	42 (50.6%)
Overweight (25–29.9)	165 (32.7%)	27 (32.5%)
Obese (≥30)	44 (8.7%)	9 (10.8%)
Etiology			0.605
Alcohol	120 (23.8%)	15 (18.1%)
Hepatitis A	19 (3.8%)	5 (6.0%)
Hepatitis B	273 (54.1%)	45 (54.2%)
Hepatitis C	33 (6.5%)	6 (7.2%)
Autoimmune	21 (4.2%)	6 (7.2%)
Drug & Toxin	11 (2.2%)	3 (3.6%)
Cryptogenic	28 (5.5%)	3 (3.6%)
Hepatocellular carcinoma	238 (47.1%)	18 (21.7%)	<0.001
Beyond Milan criteria	7 (2.9%)	9 (50.0%)	<0.001
Comorbidity
Diabetes mellitus	132 (26.1%)	21 (25.3%)	0.872
Hypertension	104 (20.6%)	13 (15.7%)	0.297
MELD score (point)	13 (8–22)	28 (16–38)	< 0.001
eGFR based kidney function grade			0.001
Stage 1	246 (48.7%)	31 (37.3%)
Stage 2	110 (21.8%)	12 (14.5%)
Stage 3a	34 (6.7%)	4 (4.8%)
Stage 3b	25 (5.0%)	11 (13.3%)
Stage 4	28 (5.5%)	4 (4.8%)
Stage 5	62 (12.3%)	21 (25.3%)
Hepatic decompensation
Encephalopathy (West Haven grade I or II)	43 (8.5%)	11 (13.3%)	0.166
Varix	124 (24.6%)	20 (24.1%)	0.928
Ascites	227 (45.0%)	50 (60.2%)	0.010
Transthoracic echocardiography
Ejection fraction (%)	65 (62–67)	65 (63–67)	0.310
Diastolic dysfunction	221 (43.8%)	33 (39.8%)	0.495
Laboratory variables
Hemoglobin (g/dL)	9.8 (8.4–11.7)	9.0 (8.1–11.3)	0.056
WBC count (× 109/L)	4.1 (2.7–6.2)	7.8 (3.8–12.0)	<0.001
Neutrophil to lymphocyte ratio (%)	244.3 (153.0–505.2)	595.1 (301.0–1044.6)	<0.001
C-reactive protein to albumin ratio (%)	10.3 (3.2–42.5)	55.0 (20.9–134.1)	<0.001
C-reactive protein (mg/dL)	0.3 (0.1–1.2)	1.5 (0.7–4.0)	<0.001
Albumin (g/dL)	3.0 (2.7–3.5)	2.8 (2.5–2.9)	<0.001
Platelet count (× 109/L)	63.0 (46.0–103.0)	62.0 (39.0–87.0)	0.285
Sodium (mEq/L)	139.0 (135.0–142.0)	138.0 (133.0–141.0)	0.023
Potassium (mEq/L)	4.0 (3.7–4.3)	3.9 (3.5–4.3)	0.182
Calcium (mg/dL)	8.4 (8.0–8.8)	8.4 (7.9–8.8)	0.504
Glucose (mg/dL)	108.0 (92.0–136.5)	123.0 (96.0–156.0)	0.035
Ammonia (μg/dL)	98.0 (66.0–153.5)	93.0 (67.0–149.0)	0.635

Abbreviations: EAD, early allograft dysfunction; eGFR, estimated glomerular filtration rate; CRRT, continuous renal replacement therapy; MELD, Model for End-stage Liver Disease; WBC, white blood cell

NOTE: Values are medians (interquartile range) or numbers (proportion).

Table 2

Intraoperative recipient and donor-graft findings of the non-EAD and EAD groups.

Group	non-EAD	EAD	p
n	505	83
Intraoperative recipient findings
Surgical duration (min)	500 (450–565)	510 (470–590)	0.213
Postreperfusion syndrome	108 (21.4%)	29 (34.9%)	0.007
Average of vital signs
MBP (mmHg)	74 (69–80)	75 (65–81)	0.747
HR (beats/min)	89 (80–99)	94 (83–107)	0.013
CVP (mmHg)	9 (7–11)	9 (7–12)	0.548
Mean lactate (mmol/L)	3.7 (2.9–4.9)	3.8 (2.6–5.5)	0.855
Blood product transfusion (unit)
Packed red blood cells	7 (4–13)	11 (8–16)	< 0.001
Fresh frozen plasma	7 (4–10)	10 (8–15)	< 0.001
Single donor platelet	1 (0–2)	1 (0–2)	0.002
Cryoprecipitate	0 (0–0)	0 (0–0)	0.017
Hourly fluid infusion (mL/kg/h)	9.6 (6.7–12.9)	9.5 (6.4–13.6)	0.645
Hourly urine output (mL/kg/h)	1.3 (0.7–2.1)	1.0 (0.3–1.7)	0.001
Doppler ultrasonography
Hepatic arterial resistive index	0.64 (0.63–0.66)	0.64 (0.64–0.67)	0.936
Portal venous flow (mL/min)	2180.2 (1749.5–2281.3)	2179.1 (1647.0–2183.1)	0.394
Donor-graft findings
Age (years)	35 (26–40)	35 (31–46)	0.017
Sex (male)	344 (68.1%)	52 (62.7%)	0.325
Body mass index (kg/m2)	23.8 (21.8–25.4)	23.8 (22.3–25.2)	0.990
GRWR (%)	1.2 (1.0–1.5)	1.2 (1.0–1.5)	0.964
Graft ischemic time (min)	93 (69–122)	113 (74–192)	0.002
Fatty change (%)	4.7 (1.0–5.0)	4.7 (1.0–5.0)	0.341

Abbreviations: EAD, early allograft dysfunction; GRWR, graft recipient weight ratio; MBP, mean blood pressure; HR, heart rate; CVP, central venous pressure

NOTE: Values are medians (interquartile range) or numbers (proportion).

Comparison of predictive accuracy for EAD development among inflammatory markers

The predictive accuracy of CRP/ALB was found to be higher than that of other inflammatory markers, such as CRP, ALB, WBC count, and NLR (Table 3). The optimal CRP/ALB ratio cutoff for prediction of EAD development was 20% (AUC: 0.722; 95% CI: 0.648–0.758; p < 0.001).

Table 3

Predictive accuracy of inflammatory markers for EAD development.

	AUC	95% CI	p
C-reactive protein to albumin ratio (%)	0.722	0.684–0.758	< 0.001
C-reactive protein (mg/dL)	0.711	0.672–0.747	< 0.001
Albumin (g/dL)	0.670	0.630–0.708	< 0.001
WBC count (× 109/L)	0.672	0.632–0.710	< 0.001
Neutrophil to lymphocyte ratio (%)	0.717	0.679–0.753	< 0.001

Abbreviations: AUC, area under the curve; WBC, white blood cell

Association of pre- and intraoperative findings with EAD development

In multivariate logistic regression (Table 4), CRP/ALB ratio was significantly associated with EAD development, together with the MELD score, requirement of FFP, and donor age (AUC: 0.793; 95% CI: 0.757–0.825; sensitivity: 79.5%; specificity: 71.7%; p < 0.001). Furthermore, the probability of EAD development in patients with a CRP/ALB ratio > 20% was 2-fold higher than in those with a CRP/ALB ratio ≤ 20% (odds ratio: 2.158; 95% CI: 1.131–4.114; p = 0.02; Table 4). In the EAD group (n = 83), the prevalence of patients with a CRP/ALB ratio > 20% was 75.9% (n = 63), while in the non-EAD group (n = 505), the prevalence of a CRP/ALB ratio > 20% was only 37.0% (n = 187).

Table 4

Association of pre- and intraoperative recipient and donor-graft findings with EAD development.

	Univariable logistic regression analysis				Multivariable logistic regression analysis
	β	Odds ratio	95% CI	p	β	Odds ratio	95% CI	p
Preoperative recipient finding
Age (years)	-0.022	0.978	0.953–1.005	0.106
Sex (male vs. female)	0.086	1.090	0.660–1.800	0.737
Body mass index (kg/m2)	-0.026	0.974	0.915–1.037	0.409
Comorbidity
Diabetes mellitus	-0.044	0.957	0.562–1.631	0.872
Hypertension	-0.334	0.716	0.381–1.344	0.299
MELD score (point)	0.083	1.087	1.064–1.110	<0.001	0.063	1.065	1.040–1.090	<0.001
eGFR based kidney function grade	0.206	1.229	1.093–1.381	0.001
Hepatic decompensation
Encephalopathy	0.496	1.641	0.809–3.330	0.170
Varix	-0.025	0.975	0.567–1.678	0.928
Ascites	0.618	1.856	1.156–2.979	0.010
Transthoracic echocardiography
Ejection fraction (%)	0.031	1.031	0.977–1.088	0.262
Diastolic dysfunction	-0.165	0.848	0.528–1.362	0.495
Laboratory variables
Hemoglobin (g/dL)	-0.095	0.909	0.815–1.015	0.090
WBC count (x 109/L)	0.076	1.079	1.039–1.120	<0.001
Neutrophil to lymphocyte ratio (%)	0.056	1.057	1.025–1.091	0.001
CRP/ALB (%) (continuous)	0.008	1.008	1.005–1.011	<0.001	0.004	1.004	1.001–1.007	0.004
CRP/ALB (%) (dichotomized)*
≤ 20%	reference
> 20%	1.678	5.357	3.139–9.142	<0.001	0.769	2.158	1.131–4.114	0.020
C-reactive protein (mg/dL)	0.192	1.211	1.101–1.332	<0.001
Albumin (g/dL)	-1.160	0.313	0.195–0.504	<0.001
Platelet count (x 109/L)	-0.002	0.998	0.993–1.002	0.313
Sodium (mEq/L)	-0.045	0.956	0.917–0.996	0.032
Potassium (mEq/L)	-0.196	0.822	0.554–1.219	0.329
Calcium (mg/dL)	-0.031	0.970	0.737–1.276	0.826
Glucose (mg/dL)	0.002	1.002	0.998–1.005	0.368
Ammonia (μg/dL)	-0.001	0.999	0.996–1.002	0.567
Intraoperative recipient finding
Surgical duration (min)	0.001	1.001	0.999–1.004	0.291
Postreperfusion syndrome	0.680	1.974	1.199–3.251	0.008
Average of vital signs
MBP (mmHg)	-0.002	0.998	0.973–1.024	0.871
HR (beats/min)	0.022	1.023	1.006–1.039	0.007
CVP (mmHg)	0.029	1.029	0.958–1.106	0.436
Mean lactate (mmol/L)	0.055	1.056	0.997–1.119	0.062
Blood product transfusion (unit)
Packed red blood cell	0.039	1.040	1.017–1.063	0.001
Fresh frozen plasma	0.067	1.069	1.038–1.101	<0.001	0.041	1.042	1.007–1.078	0.019
Single donor platelet	0.077	1.080	1.000–1.167	0.050
Cryoprecipitate	0.094	1.099	1.004–1.203	0.042
Hourly fluid infusion (mL/kg/h)	-0.001	0.999	0.975–1.024	0.966
Hourly urine output (mL/kg/h)	-0.364	0.695	0.541–0.894	0.005
Doppler ultrasonography
Hepatic arterial resistive index	-0.140	0.869	0.024–31.114	0.939
Portal venous flow (mL/min)	0.000	1.000	1.000–1.000	0.931
Donor-graft finding
Age (years)	0.026	1.027	1.006–1.047	0.009	0.023	1.023	1.001–1.047	0.041
Sex(male)	0.242	1.274	0.786–2.064	0.326
Body mass index (kg/m2)	-0.016	0.984	0.909–1.064	0.682
GRWR (%)	0.337	1.401	0.770–2.548	0.270
Graft ischemic time (min)	0.004	1.004	1.002–1.006	<0.001
Fatty change (%)	0.003	1.003	0.969–1.038	0.865

Odds ratio of CRP/ALB (%) (dichotomized)* was a value from another univariable and multivariable logistic regression model without CRP/ALB (continuous).

Abbreviations: EAD, early allograft dysfunction; MELD, model for end-stage liver disease; eGFR, estimated glomerular filtration rate; CRRT, continuous renal replacement therapy; CRP/ALB, C-reactive protein to albumin ratio; GRWR, graft-recipient-weight-ratio; MBP, mean blood pressure; HR, heart rate; CVP, central venous pressure

Comparison of postoperative outcomes between patients with and without EAD

Patients with EAD had a longer duration of hospitalization and higher rates of poor kidney function, infection, and re-transplantation due to graft failure, as well as higher overall mortality, than those without EAD (Table 5). Patients with a CRP/ALB ratio > 20% had a longer duration of hospitalization and higher rates of poor kidney function, infection, and re-transplantation due to graft failure, as well as higher overall mortality, than those with a CRP/ALB ratio ≤ 20% (S1 Table).

Table 5

Postoperative outcomes of the non-EAD and EAD groups.

Group	non-EAD	EAD	p
n	505	83
Hospital stay (day)	25 (21–35)	31 (22–54)	0.002
During follow-up period
eGFR based kidney function grade			<0.001
Stage 1	365 (72.7%)	31 (40.3%)
Stage 2	76 (15.1%)	15 (19.5%)
Stage 3a	24 (4.8%)	9 (11.7%)
Stage 3b	26 (5.2%)	14 (18.2%)
Stage 4	8 (1.6%)	5 (6.5%)
Stage 5	3 (0.6%)	3 (3.9%)
Ascites	171 (33.9%)	24 (28.9%)	0.375
Infection	36 (7.1%)	20 (24.1%)	<0.001
Graft rejection	99 (19.6%)	17 (20.5%)	0.852
de novo Cancer occurrence	38 (7.5%)	6 (7.2%)	0.924
Re-transplantation	12 (2.4%)	12 (14.5%)	<0.001
Overall patient mortality	58 (11.5%)	30 (36.1%)	<0.001

Abbreviations: EAD, early allograft dysfunction; eGFR, estimated glomerular filtration rate

NOTE: Values are expressed as median (interquartile) and number (proportion).

Discussion

The main findings of our study were that a higher CRP/ALB ratio was independently associated with the risk of EAD development after LDLT, together with the MELD score, requirement for FFP transfusion, and donor age. Based on the CRP/ALB ratio cutoff of (> 20%) for EAD, the probability of EAD development was significantly (2-fold) higher in patients with a CRP/ALB ratio > 20% than in those with a ratio ≤ 20%. Compared to other inflammatory markers, the predictive utility of the CRP/ALB ratio for EAD development was higher.

EAD occurs in about 20% of patients who undergo LT [5,7], and 14.1% of our patients experienced this complication. EAD pathogenesis is potentially related to inflammatory and oxidative stress in the transplanted graft in response to ischemia–reperfusion injury [9,10,12]. Many studies have reported that EAD development negatively affected postoperative outcomes, resulting in short- and long-term kidney dysfunction, prolonged hospital stay, early liver graft loss, and poor patient survival [5-7,47]. Our results agree with these findings, in that patients with EAD had higher incidences of poor kidney function and infection, longer hospital stays, and re-transplantation due to graft failure, and worse overall patient mortality rate than those without EAD. A previous study by Wadei et al.[47] indicated an association of EAD occurrence with new acute kidney injury requiring renal replacement therapy within the first month and end-stage renal disease within the first year after LT. They speculated that the development of EAD contributed to an increase in oxidative stress due to the production of reactive oxygen species and triggered a systemic inflammatory response that expanded beyond the liver graft.

In critically ill patients, CRP/ALB ratio reflects both inflammatory activation and nutritional deficiency [48,49], and has gradually been accepted as an emerging prognostic marker of morbidity and mortality [13,14]. CRP level increases during complex and stressful surgeries, as well as in numerous diseases, such as sepsis, decompensated heart failure, and cerebral disease [19-21,50]. In patients with chronic liver disease [51-57], a higher serum CRP concentration serves as an independent prognostic marker related to morbidity and mortality. In a study of Escherichia coli infection, the host capacity for CRP production was maintained in cirrhotic patients with severe liver dysfunction [58]. Another infection study suggested that serum levels of acute-phase proteins (CRP and procalcitonin) originating from the liver were comparable between patients with and without cirrhosis [59]. Recent studies have suggested that CRP can serve as a surrogate biomarker for acute or chronic systemic inflammation, which may be poorly predicted by the MELD score in patients with ESLD, such as alcoholic hepatitis, hepatocellular carcinoma, tissue necrosis, and bacterial translocation. Furthermore, increased CRP was significantly associated with patient outcomes such as hepatic insult and/or extrahepatic organ dysfunction [56,60]. Although CRP is largely synthesized in the liver, other cells (smooth muscle cells, macrophages, endothelial cells, lymphocytes, and adipocytes) and reserved hepatocytes seem to be able to produce CRP in response to increasing IL-6, which is continuously activated by lipopolysaccharide-binding protein during cirrhosis [61-63]. Additionally, CRP plays critical roles in the host response to infection and inflammation, such as the complement pathway, recruitment of leukocytes, facilitation of apoptosis and phagocytosis, and production of nitric oxide and cytokines [23].

Hypoalbuminemia is commonly seen in septic patients and is associated with the severity of sepsis [64]. A decrease in serum ALB level of 10 g/L is associated with increased risks of mortality and morbidity, and prolonged ICU and hospital stays [65]. Circulating albumin has been considered as an estimation tool for hepatic insufficiency as a component of the Child-Pugh classification [27]. Additionally, because circulating albumin plays a role in scavenging and disposing of inflammatory mediators such as cytokines and lipopolysaccharide, a low albumin level may contribute to the aggravation of inflammatory activation [66]. Compared to other more well-established indicators of inflammation (e.g., the Glasgow Prognostic Score [GPS], modified GPS, NLR, platelet-lymphocyte ratio, prognostic index, and prognostic nutritional index), CRP/ALB ratio was a better predictor of poor overall patient survival [67]. However, a study of ICU patients suggested that the predictive accuracy of CRP/ALB ratio for 30-day mortality did not exceed that of the ALB level alone, the Acute Physiologic Assessment and Chronic Health Evaluation II, or the Charlson Comorbidity Index [68]. However, because patients admitted to the ICU due to mixed and heterogenous causes were enrolled in the study by Oh et al. [68], the results may have limited relevance for specific cases such as cirrhosis, malignancy, or infection.

Our results are supported by those from previous studies of chronic liver disease [51,53] showing that an increased CRP/ALB ratio was significantly associated with the severity of hepatic inflammation and prognosis. Our patients with EAD showed higher levels of inflammatory markers (i.e., WBC count, NLR, CRP/ALB ratio, CRP, and ALB) than those without EAD. In a multivariate regression analysis, a higher CRP/ALB ratio remained an independent predictor of EAD occurrence after LDLT, and the AUC of the CRP/ALB ratio was higher than other inflammatory indicators, such as NLR. Therefore, the predictive utility of the CRP/ALB ratio for EAD development is likely to be high, and the magnitude of the CRP/ALB ratio may be related to the inflammatory and metabolic demand of the liver graft, and thus the risk of EAD development. Additionally, previous studies have suggested that antiviral treatment leads to significant amelioration of the MELD score and an improved portal hypertension-related prognosis in patients with HBV-related decompensated cirrhosis [69,70]. An HBV study by Huang et al.[53] found that the CRP/ALB ratio decreased significantly in response to antiviral therapy. This suggests that antiviral therapy influences the expected capacity of the CRP/ALB ratio, which should be confirmed in future studies investigating the dose and timing of antiviral therapy in other types of hepatitis.

Our study, supported by Olthoff et al.[7], suggests that MELD score and donor age are associated significantly with the risk of EAD occurrence within the first week after LT. Poor implanted liver graft function may contribute to the persistence of a preoperatively high MELD score, including alterations of the total bilirubin level, international normalized ratio, and creatinine level, until postoperative day 7. In addition, donor age seems to have an impact on the initiation of the molecular repair pathway, and solid (i.e., liver, lung, heart, and kidney) grafts from older donors exhibit prolonged functional recovery more frequently than do those from younger donors [71]. In patients undergoing LDLT, grafts from younger donors have better vascular resistance, higher compliance of the hepatic parenchyma, and more favorable regeneration than those from older donors. Donor age is thus a critical and independent factor in recipient survival [72,73].

In our study, a greater requirement for FFP transfusion was a prognostic factor for the occurrence of EAD. Wadei et al.[47] reported that patients with EAD required greater amounts of blood product (including FFP) transfusion than did those without EAD. As persistent uncontrolled coagulopathy be an early sign of transplanted graft dysfunction [74], it is not surprising that the requirement for FFP transfusion was higher in the EAD group than in the non-EAD group. Poor liver graft recovery seems to begin with severe ischemia–reperfusion injury, followed by the continuous presence of coagulopathy [75].

This study has some limitations. First, we were not able to clarify the underlying mechanisms. Although both CRP and ALB reflect systemic inflammation, further prospective studies are required to elucidate the pathophysiological processes underlying the association of the CRP/ALB ratio with EAD. As albumin has a positive impact on homeostasis, including the stabilization of endothelial glycocalyx [76], the development of a clinical algorithm may advance therapeutic practice. Second, there are characteristic differences between LT from living and deceased donors. LDLT allografts are partial livers from healthy donors (i.e., smaller but with a healthy status), while DDLT allografts are whole livers from deceased donors with poorer clinical conditions and prolonged graft cold ischemic times (i.e., larger but with some injury) [5,7]. Therefore, the impact of donor-graft factors on the development of EAD may have been reduced in our LDLT study. Additional studies are required to validate the predictive role of the CRP/ALB ratio for EAD in LT not only from living donors, but also from deceased donors. Third, the incidence of EAD was lower in patients with than in those without HCC, but higher in the HCC beyond the Milan criteria group than in the HCC within the Milan criteria group. As this finding may reflect selection bias, we did not analyze the association of HCC with EAD occurrence. Further studies are required to investigate the associations only in patients with HCC undergoing LDLT. Fourth, because of the retrospective study design, not all potential confounding factors could be removed. Finally, although clinical factors related to EAD were controlled for in multivariate analysis, the possibility of selection bias could not be completely excluded, and the results should be interpreted carefully.

Conclusions

Our study showed that CRP/ALB ratio, measured prior to LDLT, was an independent predictor of EAD development, together with a high MELD score, greater requirement for FFP transfusion, and older donor age. Therefore, the easily calculated CRP/ALB ratio may allow estimation of the risk of EAD after LDLT and can provide additional information that may facilitate the overall estimation of a patient’s condition.

Postoperative outcomes of patients with CRP/ALB ratios ≤ and > 20%.

(DOCX)

Click here for additional data file.

16 Sep 2019

PONE-D-19-22048

Predictive utility of the C-reactive protein to albumin ratio in early allograft dysfunction in living donor liver transplantation: A retrospective observational cohort study

PLOS ONE

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Reviewer #1: Chae et al. evaluated relationship between preoperative CRP/Alb and EAD after LDLT in their study population of 588 patients. They find patients with CRP/Alb >20% showed 2-fold higher incidence of EAD. Further, patients with higher CRP/Alb showed poorer overall survival than those with lower CRP/Alb. They concluded higher CRP/alb could predict EAD after LDLT. We think this result is somehow understandable. However, we found some issues.

major

1. First of all, CRP and Alb are both generated in the liver. Can we simply trust the values of CRP as an inflammatory parameter in patients with ESLD? The authors should explain this point.

2. This is two stage story (high CRP/alb=>EAD=>graft failure). Although the authors showed correlation between high CRP/alb and EAD by multivariate analysis, they did not prove correlation between EAD and graft failure correctly because the graph they showed us was simple univariate analysis (Fig 1). We found significantly higher pre-operative risks in EAD group (background disease, MELD score, ischemia time). The same thing in Fig 2. If they want to show this result, they should perform propensity score matching showing higher CRP/alb could lead to graft failure or EAD. Also, how was the results of Cox-regression analysis, using CRP/Alb for graft failure?

3. The authors focus on EAD. Why did the authors showed overall survival? not graft survival in Fig 1 and 2?

4. Why could the authors find donor factors being the risk for EAD? We could not simply accept only one recipient preoperative parameter can be indicator for EAD and graft loss (including long-term patient survival). They should refer this point at discussion, not only one sentence as a limitation since many previous articles focused on donor factors in LDLT.

5. As an objective parameter, “intraoperative portal pressure (or portal flow) after reperfusion “ is very important since it is well-known factor for developing “small for size syndrome”.

6. In addition to EAD, how was the postoperative complications, such as ascites, infection, etc (makers for small for size syndrome) in high CRP/alb ?

7. Since CRP/alb is preoperative parameter, if they find CRP/alb>20, what do they do? Do they treat them with antibiotics? Have the patinet better nutritional condition before preceding to transplant? They should discuss this point.

Minor

1. Table 1, they should stratify BMI because we don’t believe BMI will show liner relationship with EAD.

Reviewer #2: This study was performed to determine the association between the ratio of C-reactive protein to albumin (CRP/ALB) and the risk of early allograft dysfunction(EAD) in patients undergoing living donor liver transplantation (LDLT).The easily calculated CRP/ALB ratio may allow estimation of the risk of

EAD after LDLT and can provide additional information that may facilitate overall estimation of the patient’s condition.

The manuscript is written well but there are several concerns.

comments.

1. In table 3, The predictive accuracy of CRP/ALB was found to be higher than that of other inflammatory

markers, such as CRP, ALB, WBC count, and NLR. But in table 4, among inflammatory markers, CRP only nor ALB are not listed. The authors should list up CRP and ALB independently.

2. In table 5, Patients with EAD had a longer duration of hospitalization and higher incidence rates of poor kidney function and infection than those without EAD. These postoperative conditions such as poor kidney function and infection cause EAD? If these postoperative parameters included in multivariable logistic regression, how about significancy?

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Reviewer #2: Yes: Soichiro Murata

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2 Nov 2019

A point-by-point response letter

Yun-Wen Zheng

Academic Editor

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Dear Dr. Zheng:

We are pleased to have had the opportunity to revise and resubmit our manuscript. We would like to thank the reviewers for their insightful comments, which have helped to significantly improve our manuscript. Our point-by-point responses to each comment are presented below. Our revisions and responses are provided directly after each comment. The revised parts of the manuscript are shown using tracked changes.

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Reviewers’ comments

Reviewer #1: Chae et al. evaluated relationship between preoperative CRP/Alb and EAD after LDLT in their study population of 588 patients. They find patients with CRP/Alb >20% showed 2-fold higher incidence of EAD. Further, patients with higher CRP/Alb showed poorer overall survival than those with lower CRP/Alb. They concluded higher CRP/alb could predict EAD after LDLT. We think this result is somehow understandable. However, we found some issues.

major

1. First of all, CRP and Alb are both generated in the liver. Can we simply trust the values of CRP as an inflammatory parameter in patients with ESLD? The authors should explain this point.

Response: The outcome and reversibility of hepatic decompensation vary according to the nature and severity of the acute hepatic insult, and according to the degree of dysfunction of extrahepatic organ systems. Recent studies have shown that, in acutely ill patients with cirrhosis, systemic inflammatory response syndrome (SIRS) with or without a bacterial infection is an independent predictor of survival and is associated with the development of portal hypertension-related complications. Liver function appears not be the main determinant of outcome in patients with cirrhosis who experience multiorgan failure. Therefore, the negative impact of systemic inflammation may be poorly predicted by MELD scores. Conventional parameters for diagnosing SIRS lack sensitivity and specificity in patients with advanced cirrhosis because of hypersplenism, hyperventilation associated with encephalopathy, hyperkinetic circulation, or the use of beta-blockers.

Previous studies suggested that high CRP levels are often observed in patients with advanced liver failure. CRP can be used as a surrogate biomarker for acute or chronic systemic inflammation in patients with ESLD, such as alcoholic hepatitis, hepatocellular carcinoma, tissue necrosis, and bacterial translocation, and high CRP is significantly associated with patient outcome. Although CRP is largely synthesized by the liver, other cells (e.g., smooth muscle cells, macrophages, endothelial cells, lymphocytes, and adipocytes) and reserved hepatocytes seem to be able to effectively and promptly produce CRP as an acute-phase protein, mainly in response to increasing interleukin-6, which is continuously activated by the lipopolysaccharide-binding protein during cirrhosis. Hence, we consider measuring CRP to be a simple and accurate way of diagnosing systemic inflammation and providing an indication of prognosis in cirrhotic patients.

A decrease in serum albumin level is associated with a high risk of patient morbidity and mortality. Circulating albumin has been used to estimate hepatic insufficiency as a component of the Child-Pugh classification. Additionally, because circulating albumin plays a role in scavenging and disposing of inflammatory mediators, such as cytokines and lipopolysaccharides, a low albumin level may contribute to the aggravation of inflammatory activation.

Our results are supported by previous studies of chronic liver disease showing that a higher CRP/ALB ratio is significantly associated with the severity of hepatic inflammation and prognosis. Our patients with EAD showed higher levels of inflammatory markers (e.g., WBC count, NLR, CRP/ALB ratio and CRP) than those without EAD. In a multivariate regression analysis, increased CRP/ALB ratio remained an independent predictor of EAD occurrence after LDLT, and the AUC of the CRP/ALB ratio was higher than other inflammatory indicators, such as NLR. Therefore, the predictive utility of the CRP/ALB ratio for EAD development is likely to be high, and the magnitude of the CRP/ALB ratio may be related to the inflammatory and metabolic demand of the liver graft, and thus the risk of EAD (Discussion; pages 28 - 29).

2. This is two stage story (high CRP/alb=>EAD=>graft failure). Although the authors showed correlation between high CRP/alb and EAD by multivariate analysis, they did not prove correlation between EAD and graft failure correctly because the graph they showed us was simple univariate analysis (Fig 1). We found significantly higher pre-operative risks in EAD group (background disease, MELD score, ischemia time). The same thing in Fig 2. If they want to show this result, they should perform propensity score matching showing higher CRP/alb could lead to graft failure or EAD. Also, how was the results of Cox-regression analysis, using CRP/Alb for graft failure?

Response: We compared the overall survival rates between patients with and without EAD occurrence (Fig. 1) and between patients with CRP/ALB ratios ≤ 20% and > 20% (Fig. 2) using a univariate analysis (Kaplan-Meier analysis with the log-rank test). The primary aim of our study was to investigate the association of perioperative clinical factors, including CRP/ALB ratio, with EAD occurrence, and additionally to compare postoperative outcomes, including overall patient survival, between patients with and without EAD. The analysis of risk factors for overall survival, including CRP/ALB ratio, is beyond the scope of this study. Therefore, we deleted the redundant Figures 1 and 2 and added the incidence of re-transplantation due to graft failure and overall patient mortality using the χ2 test or Fisher’s exact test, as appropriate, in Table 5 (pages 25 - 26). In future, we will investigate the predictive role of the CRP/ALB ratio in patient or graft survival after LDLT.

3. The authors focus on EAD. Why did the authors showed overall survival? not graft survival in Fig 1 and 2?

Response: We focused on predictive factors, including the CRP/ALB ratio, for EAD occurrence. We also compared postoperative outcomes, such as overall patient survival, between patients with and without EAD. Because of the retrospective study design, we were not able to analyze the causes of patient mortality in detail, so we focused on the prevalence of all-cause patient mortality. On re-analysis, because re-liver transplantation was sometimes performed due to graft failure, we investigated the incidence of re-transplantation as a graft failure marker (Table 5). We have deleted the redundant Figures 1 and 2 and added the incidence of re-transplantation due to graft failure and overall patient mortality using the χ2 test or Fisher’s exact test, as appropriate, in Table 5 (pages 25 - 26).

4. Why could the authors find donor factors being the risk for EAD? We could not simply accept only one recipient preoperative parameter can be indicator for EAD and graft loss (including long-term patient survival). They should refer this point at discussion, not only one sentence as a limitation since many previous articles focused on donor factors in LDLT.

Response: Donor-graft factors play a critical role in EAD occurrence after liver transplantation. We analyzed the relationship of donor-graft characteristics, such as age, sex, BMI, graft-recipient weight ratio, graft ischemic time, and fatty change, with EAD occurrence (Tables 2 and 4; pages 17, 18 and 24). A multivariate analysis showed that increased donor age had a negative impact on early postoperative graft recovery. Previous LDLT studies suggested that grafts from younger donors had better vascular resistance, higher compliance of the hepatic parenchyma, and more favorable regeneration than those from older donors. Consequently, donor age was a critical and independent factor in recipient survival (Discussion; page 30).

Our study population consisted of patients who underwent LDLT. Because there are characteristic differences between LT from living (i.e., smaller but healthy) and deceased (i.e., larger but with some injury) donors, the impact of donor-graft factors on EAD occurrence may be not comparable between both types of LT. Therefore, additional studies are required to validate the predictive role of the CRP/ALB ratio for EAD in LT not only from living donors, but also from deceased donors (Limitations; page 31).

5. As an objective parameter, “intraoperative portal pressure (or portal flow) after reperfusion “ is very important since it is well-known factor for developing “small for size syndrome”.

Response: We investigated intraoperative data on the hepatic arterial resistive index and portal flow. The Doppler ultrasonographic findings (i.e., hepatic artery resistive index and portal venous flow) were comparable between the non-EAD and EAD groups (Table 2; page 17), and there was no statistical association of these Doppler findings with EAD occurrence (Table 4; page 24). Our results disagree with those of previous studies that identified an association between hepatic flow and EAD occurrence. This may be because of the regular assessment of hepatic vascular flow and appropriate implementation of surgical modulation during surgery. During LDLT, after completion of the hepatic vascular and ductal anastomoses (hepatic vein, portal vein, hepatic artery, and bile duct in a serial manner), the patency of the hepatic vascular flow (portal venous flow and hepatic arterial resistive index) was assessed using Doppler ultrasonography (Prosound SSD-5000; Hitachi Aloka Medical, Tokyo, Japan). Surgical inflow modification using splenectomy, splenic artery ligation, or a portocaval shunt was performed based on the discretion of the transplant surgeons (Patients and Methods; page 8).

6. In addition to EAD, how was the postoperative complications, such as ascites, infection, etc (makers for small for size syndrome) in high CRP/alb ?

Response: We compared the postoperative complications, including ascites and infection, between patients with a CRP/ALB ratio ≤ and > 20%. Patients with a CRP/ALB ratio > 20% had a longer duration of hospitalization and higher incidences of poor kidney function, infection, and re-transplantation due to graft failure, as well as higher overall mortality, than those with a CRP/ALB ratio ≤ 20% (S1 Table; page 25).

S1 Table. Postoperative outcomes of patients with CRP/ALB ratios ≤ and > 20%

Group CRP/ALB ratio ≤ 20% CRP/ALB ratio > 20% p

n 340 256

Hospital stay (days) 25 (21–34) 28 (21–43) 0.006

During follow-up period

eGFR-based kidney function grade < 0.001

Stage 1 263 (77.4%) 144 (56.3%)

Stage 2 50 (14.7%) 44 (17.2%)

Stage 3a 11 (3.2%) 23 (9.0%)

Stage 3b 11 (3.2%) 31 (12.1%)

Stage 4 3 (0.9%) 10 (3.9%)

Stage 5 2 (0.6%) 4 (1.6%)

Ascites 107 (31.5%) 88 (34.4%) 0.454

Infection 25 (7.4%) 32 (12.5%) 0.034

Graft rejection 72 (21.2%) 44 (17.2%) 0.223

De novo cancer occurrence 26 (7.6%) 18 (7.0%) 0.776

Re-transplantation 5 (1.5%) 19 (7.4%) < 0.001

Overall patient mortality 35 (10.3%) 55 (21.5%) < 0.001

NOTE: Values are expressed as the median (interquartile) and number (proportion).

7. Since CRP/alb is preoperative parameter, if they find CRP/alb>20, what do they do? Do they treat them with antibiotics? Have the patinet better nutritional condition before preceding to transplant? They should discuss this point.

Response: Because chronic inflammation was potentially associated with cirrhosis and damage-associated molecular patterns may originate from hepatocytic injury, including sterile inflammation, our study excluded patients with preoperative signs of infection. Previous studies have shown that in patients with hepatitis B virus (HBV)-related decompensated cirrhosis, antiviral treatment leads to significant downregulation of the MELD score; it is now generally recognized that antiviral therapy can improve the prognosis of HBV-related cirrhosis. An HBV study by Huang et al. (reference No. 53; page 41 - 42) suggested that the CRP/ALB ratio was also significantly downregulated in response to antiviral therapy. This suggests that antiviral therapy influences the predictive capacity of the CRP/ALB ratio. Further research is required to investigate the dose and timing of antiviral therapy in other types of hepatitis (Discussion; pages 29 - 30).

Minor

1. Table 1, they should stratify BMI because we don’t believe BMI will show liner relationship with EAD.

Response: As per the reviewer’s comments, we compared the stratified BMI values between patients with and without EAD (Table 1; page 14).

Reviewer #2: This study was performed to determine the association between the ratio of C-reactive protein to albumin (CRP/ALB) and the risk of early allograft dysfunction(EAD) in patients undergoing living donor liver transplantation (LDLT).The easily calculated CRP/ALB ratio may allow estimation of the risk of EAD after LDLT and can provide additional information that may facilitate overall estimation of the patient’s condition.

The manuscript is written well but there are several concerns.

comments.

1. In table 3, the predictive accuracy of CRP/ALB was found to be higher than that of other inflammatory markers, such as CRP, ALB, WBC count, and NLR. But in table 4, among inflammatory markers, CRP only nor ALB are not listed. The authors should list up CRP and ALB independently.

Response: As per the reviewer’s comments, we added CRP and albumin to Table 4 (page 23). We had analyzed the association of clinical factors, including C-reactive protein and albumin, with EAD occurrence, and found that the CRP/ALB ratio was an independent predictor. Because of the potential for inter-correlations among CRP, ALB, and CRP/ALB ratio, we included only CRP/ALB ratio in the previous version of Table 4.

2. In table 5, Patients with EAD had a longer duration of hospitalization and higher incidence rates of poor kidney function and infection than those without EAD. These postoperative conditions such as poor kidney function and infection cause EAD? If these postoperative parameters included in multivariable logistic regression, how about significancy?

Response: As per the reviewer’s comments, we analyzed the correlation between postoperative kidney function, infection, and EAD occurrence (Table A), as well as the association between clinical factors, including postoperative kidney function and infection, and EAD occurrence (Tables B and C).

Table A. Correlation of postoperative kidney function, infection, and early allograft dysfunction

eGFR-based kidney function grade Infection

Early allograft dysfunction 0.264** 0.201**

**p=0.01 using Spearman’s method

Table B. Association of postoperative kidney function and infection with EAD occurrence in a univariate logistic regression analysis

β Odds ratio 95% CI p

eGFR-based kidney function grade 0.560 1.751 1.468–2.089 < 0.001

Infection 1.420 4.136 2.255–7.586 < 0.001

Abbreviation: eGFR, estimated glomerular filtration rate.

Table C. Association of clinical factors, including postoperative kidney function and infection, with EAD occurrence based on a multivariate logistic regression analysis. Potentially significant factors (p < 0.1) identified in the univariate analysis were entered into multivariate forward and backward logistic analyses.

Multivariate logistic regression analysis

β Odds ratio 95% CI p

Preoperative recipient finding

MELD score (point) 0.048 1.049 1.022–1.078 < 0.001

CRP/ALB (%) 0.004 1.004 1.001–1.007 0.012

Intraoperative recipient finding

Fresh frozen plasma (units) 0.038 1.038 1.001–1.077 0.041

Donor-graft finding

Age (years) 0.025 1.025 1.001–1.049 0.038

Postoperative recipient finding

eGFR-based kidney function grade 0.269 1.308 1.054–1.624 0.015

Infection 0.832 2.299 1.055–5.010 0.036

AUC=0.799; 95% CI=0.742–0.856; p < 0.001 in the predictive model.

Postoperative kidney function and infection were closely related to EAD occurrence. However, we were not able to determine whether postoperative kidney function and infection were independent predictors of EAD occurrence since they may share preoperative and intraoperative risk factors, such as blood product transfusion. A previous study by Wadei et al. (reference No. 47; pages 40 - 41) suggested that EAD after LT was associated with short- and long-term kidney function impairment. They found that EAD development causes oxidative stress due to the generation of reactive oxygen species and initiates a systemic inflammatory response that extends beyond the hepatic allograft. Thus, renal injury was a direct effect of the circulating cytokines or secondary to the systemic inflammatory response created by the EAD milieu, with the subsequent development of AKI leading eventually to end-stage renal disease. Therefore, further research is required to elucidate the effect of the postoperative development of AKI and infection on early graft function recovery in the liver transplantation setting.

We thank you and the reviewers again for your extremely valuable and insightful comments. We believe that our manuscript has been improved as a direct result of the review process. We hope that our revised manuscript is now deemed suitable for publication in PLoS ONE.

Sincerely,

Min Suk Chae, MD, PhD

Submitted filename: A point by point response letter.docx

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26 Nov 2019

Predictive utility of the C-reactive protein to albumin ratio in early allograft dysfunction in living donor liver transplantation: A retrospective observational cohort study

PONE-D-19-22048R1

Dear Dr. Chae,

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Reviewer #1: The paper “Predictive utility of the C-reactive protein to albumin ratio in early allograft dysfunction in living donor liver transplantation: A retrospective observational cohort study”. is now properly revised. The authors have answered all our comments wisely. We could not find any issues now.

Reviewer #2: The revision is well written and all of the comments were replied well. The revised version is acceptable.

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Reviewer #1: No

Reviewer #2: Yes: Soichiro Murata

3 Dec 2019

PONE-D-19-22048R1

Predictive utility of the C-reactive protein to albumin ratio in early allograft dysfunction in living donor liver transplantation: A retrospective observational cohort study

Dear Dr. Chae:

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