Utility of serum β2‐microglobulin for prediction of kidney outcome among patients with biopsy‐proven diabetic nephropathy

Abstract

AimTo examine whether serum β2‐microglobulin (β2‐MG) could improve the prediction performance for kidney failure with replacement therapy (KFRT) among patients with diabetic nephropathy (DN).MethodsPatients with biopsy‐proven DN at Nara Medical University Hospital were included. The exposure of interest was log‐transformed serum β2‐MG levels measured at kidney biopsy. The outcome variable was KFRT. Multivariable Cox regression models and competing‐risk regression models, with all‐cause mortality as a competing event, were performed. Model fit by adding serum β2‐MG levels was calculated using the Akaike information criterion (AIC). The net reclassification improvement (NRI) and integrated discrimination improvement (IDI) indexes were used to evaluate the improvement of predictive performance for 5‐year cumulative incidence of KFRT by serum β2‐MG levels.ResultsAmong 408 patients, 99 developed KFRT during a median follow‐up period of 6.7 years. A higher serum β2‐MG level (1‐unit increase in log‐transformed serum β2‐MG level) was associated with a higher incidence of KFRT, even after adjustments for previously known clinical and histological risk factors (hazard ratio [95% confidence interval {CI}]: 3.30 [1.57‐6.94] and subdistribution hazard ratio [95% CI]: 3.07 [1.55‐6.06]). The addition of log‐transformed serum β2‐MG level reduced AIC and improved the prediction of KFRT (NRI and IDI: 0.32 [0.09‐0.54] and 0.03 [0.01‐0.56], respectively).ConclusionsAmong patients with biopsy‐proven DN, serum β2‐MG was an independent predictor of KFRT and improved prediction performance. In addition to serum creatinine, serum β2‐MG should probably be measured for DN.