Association of low serum indirect bilirubin level with all-cause mortality in maintenance hemodialysis patients

Abstract

Objective: To investigate the association of low serum indirect bilirubin (IBIL) level with all-cause mortality in maintenance hemodialysis (MHD) patients. Methods: A multicenter retrospective cohort study was conducted in seven hemodialysis centers of Guizhou province. The adult outpatients who underwent hemodialysis for more than 3 months were included between June 2015 and June 2016. Demographics, baseline clinical and laboratory test results were collected. Patients were divided into 4 groups according to their baseline serum IBIL levels (interquartile range), and followed up until June 30, 2018. Kaplan-Meier method was used to compare the survival rate of each group. Cox regression model was used to analyze the association of IBIL with all-cause mortality. Results: A total of 885 hemodialysis dialysis patients with baseline IBIL data were enrolled in this study, with age of (55.4±16.2) years old, among whom 57.9% (512/885) were male. Median IBIL was 4.8 μmol/L and interquartile range was 3.3-7.0 μmol/L. The comparison between IBIL quartile groups showed that the differences in proportion of diabetics, hemoglobin, serum albumin, platelet, serum calcium, alanine aminotransferase (ALT), uric acid and urea nitrogen were statistically significant (all P<0.05). After a median follow-up of 24 months, 210 patients died, and 96 cases became lost to follow-up. Kaplan-Meier curves showed higher all-cause mortality in patients with IBIL≤3.3 μmol/L (Q1 group) (65/219, P=0.015). After adjusting for age, gender, comorbidities, and biochemical indicators, taking baseline IBIL Q2 level (IBIL 3.4~4.8 μmol/L) as a reference, the hazard ratio for all-cause death in patients with IBIL≤3.3 μmol/L was 1.661 (95%CI: 1.114-2.476, P=0.013). Kaplan-Meier survival curve showed that there was no significant difference in mortality between the quartile groups according to total bilirubin (TBIL) or direct bilirubin (DBIL) (P=0.167, 0.156). Conclusion: Baseline low serum IBIL in maintenance hemodialysis patients is associated with all-cause mortality.