Is the Adjustment of Serum Creatinine Level from < 0.6 mg/dL to 0.6 mg/dL Justified in Estimating Carboplatin Clearance Calculated by the Jelliffe Formula?

Background: In current Gynecologic Oncology Group studies, serum creatinine level is adjusted to 0.6 mg/dL in patients with levels < 0.6 mg/dL (Adjusted-Jelliffe formula). The purpose of this study is to evaluate whether this adjustment is suitable. Patients and Methods: Carboplatin clearance was estimated in 115 patients with serum creatinine < 0.6 mg/dL who received carboplatin-based chemotherapy for gynecologic malignancies between January 1996 and August 2004. The clearance was estimated using the Cockroft-Gault, Jelliffe, and Adjusted-Jelliffe formulae. The 3 estimations were then compared with each other using the post hoc Wilcoxon signed rank test. Bias was assessed by mean percentage error (MPE), and precision was assessed by mean absolute percentage error (MAPE). The relationships between body surface area (BSA) and ratios of estimated carboplatin clearance (Jelliffe formula/Cockroft-Gault formula and Adjusted-Jelliffe formula/Cockroft-Gault formula) were evaluated by simple regression analysis. Results: The carboplatin clearance calculated by the Jelliffe formula was significantly larger than the other 2 formulae (P < .0001). Although MPE was reduced from +20 to +6 by adjustment of serum creatinine, MAPE was barely reduced from 21 to 14. The simple regression line represents correlation between BSA and ratios of estimated carboplatin clearance was merely translated to below by adjusting the serum creatinine level, and the bias by BSA was not corrected. Conclusion: Despite adjusting the serum creatinine level, the Adjusted-Jelliffe formula overestimates the creatinine clearance when compared with the Cockcroft-Gault formula. [ABSTRACT FROM AUTHOR]