Can serum cystatin C reflect the glomerular filtration rate accurately in pediatric patients under chemotherapeutic treatment? A comparative study with Tc-99m DTPA two-plasma sample method

OBJECTIVE It was assessed whether cystatin C (cysC) could be used as a marker of glomerular filtration rate (GFR) by considering the technetium-99m diethylenetriamine penta-acetate (Tc-99m DTPA)-two blood sample method (GFRTc-99m DTPA) as the reference in pediatric patients under chemotherapeutic treatment. METHODS The chemotherapy group (CG) consisted of 31 patients (21 females, 10 males median age: 8.2 years; range: 2-16 years) who had been planned to receive allogenic hematopoietic stem cell transplantation. All patients in the CG received conditioning regimen (includes chemotherapy protocol) before hematopoietic stem cell transplantation. In addition, 21 patients (14 females, seven males median age: 9.5 years; range: 4-16 years) without any chemotherapy (nonchemotherapy group: nCG) were also prospectively investigated. Serum cysC, serum creatinine, GFRTc-99m DTPA, and GFR with a cysC-based formula (GFRcysC) were analyzed. Tubular function was also assessed. RESULTS Although we found good correlation between GFRTc-99m DTPA and cysC (r = -0.78), GFRTc-99m DTPA and GFRcysC (r = 0.91), cysC and creatinine (r = 0.91) in nCG, the same correlations were poor in CG (r = -0.42, r = 0.43, r = 0.46, respectively). Tubular function was impaired after chemotherapy. Bias+/-1.96 SD values were -6+/-15.7 and -3+/-54.8 ml/min/1.73 m in nCG and CG, respectively. Precision was also better in nCG (10 ml/min/1.73 m) than in CG (27.6 ml/min/1.73 m). CONCLUSION Serum cysC and GFRcysC cannot reflect GFR accurately in pediatric patients under chemotherapeutic treatment. Tubular cell damage induced by chemotherapeutics could be a responsible factor through the impairment of tubular absorption and metabolism of cysC.