RESUMO
BACKGROUND: The carboplatin (CBDCA) dosage is usually calculated using the formula of Calvert. Instead of the glomerular filtration rate (GFR), 24-h creatinine clearance (24 CLcr) is often used in this formula, which is calculated based on 24-h urine collection in clinical practice. OBJECTIVE: We studied the adequacy of 24 CLcr in calculating the appropriate dosage of CBDCA using the formula of Calvert and compared CLcr and GFR using various substitutable predictive formulas (the formulae of Cockcroft and Gault, Yasuda, Orita, Jellife, Mawer, MDRD, and modified MDRD) when we were not able to use 24 CLcr. METHODOLOGY: We retrospectively studied 193 patients who received CBDCA as chemotherapy during the period April 2004 through November 2006. We evaluated the adequacy of 24-h urine collection for measurement of creatinine production and excretion. We also evaluated the appropriate urine collection within a 15% range of the difference. The correlation between the appropriate 24 CLcr resulting in the urine collection and the CLcr or GFR was examined using past predictive formulae in the patients with appropriate urine collection. RESULTS: The accuracy of 24 CLcr was evaluated in 83 patients (43%). There was a significant correlation between CLcr or GFR using various predictive formulas and the appropriate 24 CLcr. There was an especially close and significant correlation with the formulae of Cockcroft and Gault and Yasuda (r>0.950, p<0.001). CONCLUSION: When using the Calvert formula, the accuracy of 24 CLcr should be evaluated. Patients evaluated as having inaccurate urinary collection should use the formulae of Cockcroft and Gault and Yasuda.