Serum bilirubin tied to kidney transplant outcomes

Kidney transplant recipients with low serum bilirubin levels are at greater risk of adverse outcomes, such as graft loss, graft failure, and all-cause mortality, a recent study has found.

The study included 1,628 patients who had undergone transplantations between 2003 and 2017. Through routine biochemical tests, serum bilirubin was measured monthly during the first postoperative year, and every 3 months thereafter; participants were divided into sex-specific quartiles according to these measurements. The primary outcome of interest was graft loss. Secondary endpoints included death-censored graft failure, all-cause death, and graft function.

Graft survival grew increasingly impaired with decreasing serum bilirubin levels (p<0.001). The 10-year graft survival rate was 91.5 percent in the highest quartile, dropping to 89.8 percent, 84.5 percent, and 76.8 percent in each succeeding quartile.

Death-censored graft survival was likewise significantly better among patients with high bilirubin. Compared with the highest quartile, participants in the lowest quartile of serum bilirubin saw significantly elevated risks of graft loss (hazard ratio [HR], 2.64, 95 percent confidence interval [CI], 1.67–4.18) and death-censored graft failure (HR, 2.96, 95 percent CI, 1.62–5.40).

Over the follow-up, 66 patients died. Multivariable Cox regression analysis also showed that all-cause mortality was significantly more likely in the lowest category of bilirubin (HR, 2.07, 95 percent CI, 1.01–4.22). Graft renal function, as assessed through estimated glomerular filtration rate, was likewise consistently weaker in the bottom vs top quartiles of serum bilirubin.

“To the best of our knowledge, this study represents the largest cohort study conducted to evaluate the effects of serum bilirubin on transplant outcomes after kidney transplantation,” the researchers said.