A simple method to evaluate residual renal function by spot urinary cystatin C-to-creatinine ratio in peritoneal dialysis patients

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

BACKGROUND

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).

PATIENTS AND METHODS

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.

RESULTS

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.

CONCLUSION

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

Evaluation of the serum cystatin C values in prediction of indications for hemodialysis in patients with chronic renal failure

BACKGROUND

Indications of dialysis treatment for patients with end-stage renal disease depend on various clinical and laboratory parameters. In this study, we aimed to determine whether standardized serum cystatin C (SCC) equation may be an applicability of marker for dialysis initiation and its relationship to other clearance values among patients with advanced chronic kidney disease.

MATERIALS AND METHODS

A total of 84 patients (45 males, 39 females) aged 19-89 were evaluated in this study. Hemodialysis was indicated according to clinical and laboratory findings, and estimated glomerular filtration rate (eGFR) was according to four different formulas [MDRD, EpiCKD, Cockcroft Gault formula (CGF) and SCC equation].

RESULTS

eGFR values of patients in the study were 7.23 ± 3.26, 7.86 ± 3.78, 15.09 ± 10.88 and 11.31 ± 4.54 according to MDRD, EpiCKD, SCC equation and CGF, respectively. There was a positive correlation between MDRD, EpiCKD and CGF, and between EpiCKD and CGF (p < 0.01). Also, statistically significant correlation was found between SCC equation and CGF (p < 0.05).

CONCLUSION

SCC equation was not seemed to be an appropriate marker for starting dialysis in patients with advanced CKD.

Serum cystatin C for estimation of residual renal function in children on peritoneal dialysis

Residual renal function (RRF) is an important parameter in the management of patients on chronic dialysis. The aim of this cross-sectional study was to determine the efficacy of serum cystatin C (CysC) for RRF estimation in 20 children (16 boys, 4 girls; median age 13.4 years) undergoing peritoneal dialysis (PD). For studies of correlation with serum CysC, the average of creatinine clearance rate (Ccr) and urea clearance rate (Curea), Kt/Vurea, and weekly Ccr were evaluated as parameters reflecting RRF. The serum CysC level was found to be negatively correlated with urine volume (r=-0.717, P<0.001), average of Ccr and Curea (r=-0.851, P<0.001), total and renal weekly Ccr (r=-0.795, P<0.001; r=-0.845, P<0.001, respectively), and renal Kt/Vurea (r=-0.793, P<0.001) and positively correlated with peritoneal weekly Ccr (r=0.738, P<0.001) and peritoneal Kt/Vurea (r=0.785, P<0.001). There was no significant association with total Kt/Vurea (r=-0.335, P=0.148). In non-anuric group of patients, serum CysC had no link to peritoneal Kt/Vurea (r=0.573, P=0.066), but was negatively correlated with renal Kt/Vurea (r=-0.609, P=0.047). In the multiple regression analysis, renal Kt/Vurea significantly contributed to log CysC concentration rather than peritoneal Kt/Vurea. The results of this study suggest that serum CysC could be an appropriate marker for RRF, independent of total and peritoneal Kt/Vurea.