C-terminal agrin fragment (CAF) as a serum biomarker for residual renal function in peritoneal dialysis patients

C-terminal agrin fragment (CAF, size 22 kDa) is a promising new biomarker for kidney function. This study evaluated the usefulness of CAF as a serum biomarker for residual renal function (RRF) in patients undergoing automated peritoneal dialysis (APD).

Serum, urine and dialysate samples were obtained in 12 end-stage renal disease patients undergoing APD. Total, renal and peritoneal clearances were calculated for CAF, creatinine, blood urea nitrogen (BUN) and cystatin c. kt/V was computed, and RRF (in ml/min) was calculated as the arithmetic mean of creatinine and BUN clearance. Correlations between the biomarkers' serum concentrations, clearances, kt/V and RRF were computed.

Serum CAF concentrations were highly correlated with serum concentrations of creatinine (r = 0.806, p = 0.002), BUN (r = 0.727, p = 0.007), cystatin c (r = 0.839, p = 0.001) and inversely to 24-h urinary output (r = -0.669, p = 0.017). RRF was inversely correlated with serum concentrations of CAF, cystatin c and creatinine being highest for CAF (r = -0.734, p = 0.007) followed by cystatin c (r = -0.65, p = 0.022) and creatinine (r = -0.606, p = 0.037). Serum BUN was not significantly associated with RRF (r = -0.497, p = 0.101). Age, weight and gender did not significantly affect serum CAF concentrations.

Serum CAF provides a robust serum biomarker for RRF in peritoneal dialysis patients undergoing APD, possibly outperforming the value of conventional biomarkers.