Supplementary file 1_Prognostic value of serum total bilirubin-lipid ratios in patients with IgA nephropathy.docx

Given bilirubin’s antioxidant and dyslipidemia’s pro-inflammatory roles, we hypothesized that TBIL-lipid ratios would serve as novel composite biomarkers associated with renal outcomes in IgAN.</p>Methods<p>We evaluated four serum bilirubin-lipid ratios (TBIL/Triglyceride, TBIL/Cholesterol, TBIL/HDL, TBIL/LDL) using Cox regression, restricted cubic spline (RCS), and linear mixed-effects (LME) models in biopsy-proven IgAN patients.</p>Results<p>Of the 1352 patients included in this study, 283 (20.93%) developed composite renal outcome (≥30% decline in estimated glomerular filtration rate [eGFR] or ESRD).

Multivariable Cox analysis showed that all four ratios were independently associated with reduced outcome risk: TBIL/Triglyceride (HR = 0.972, P = 0.025), TBIL/Cholesterol (HR = 0.849, P = 0.003), TBIL/HDL (HR = 0.970, P = 0.030), and TBIL/LDL (HR = 0.926, P = 0.004). Although the proportional hazards assumption was violated (all P < 0.05), time-dependent and piecewise Cox models confirmed that the protective effects remained significant in the early phase (≤3.13 years) but attenuated thereafter.