Is endogenous creatinine clearance still a reliable index of glomerular filtration rate in diabetic patients?

Three methods routinely used for estimation of renal function - plasma creatinine, endogenous creatinine clearance and estimation of endogenous creatinine clearance from plasma creatinine - are compared with the measurement of glomerular filtration rate based on a single injection of 51Cr-EDTA, a technique that was standardized for this study in 20 healthy volunteers. The different creatinine methods were compared with the 51Cr-EDTA method in 30 diabetic patients, resulting in 68 sets of data in which all four estimates were made simultaneously. Spearman's correlation values (rs) for comparing the three creatinine methods with that of 51Cr-EDTA were 0.74, 0.40 and 0.82 (P less than 0.05). It is suggested that the use of endogenous creatinine clearance to estimate the glomerular filtration rate (GFR) requires caution and the recognition of the limitations of the method, and that simpler techniques (serum creatinine or estimated endogenous creatinine clearance) are preferable in routine practice. GFR based on 51Cr-EDTA injection is the method of choice for monitoring renal function in special situations such as renal transplantation and progressive nephropathies.