24-hour creatinine clearance reliability for estimation of glomerular filtration rate in different stages of chronic kidney disease

Glomerular Filtration Rate (GFR) is considered the best overall index of renal function currently used. Measurement of 24 hours urine/plasma creatinine ratio (UV/P) is usually used for estimation of GFR. However little is known about its accuracy in different stages of Chronic Kidney Disease (CKD) aim: is to evaluate performance of UV/P in classification of CKD by comparing it with isotopic GFR (iGFR). 136 patients with CKD were enrolled in this study 80 (59%) were males, 48 (35%) were diabetics. Mean age 46 ± 13. Creatinine Clearance (Cr.Cl) estimated by UV/P and Cockroft-Gault (CG) was done for all patients, iGFR was the reference value. Accuracy of UV/P was 10%, 31%, 49% within ± 10%, ± 30%, ± 50% error respectively, r 2 = 0.44. CG gave a better performance even when we restrict our analysis to diabetics only, the accuracy of CG was 19%, 47%, 72% in ± 10%, ± 30% and ± 50% errors respectively, r 2 = 0.63. Both equations gave poor classification of CKD. In conclusion, UV/P has poor accuracy in estimation of GFR, The accuracy worsened as kidney disease becomes more severe. We conclude 24 hours CrCl. is not good substitute for measurement of GFR in patients with CKD.