CORRELATION BETWEEN 4 HOURS CREATININE CLEARANCE AND CR-51-EDTA TEST

Background Crecatinine clearance as a measure of glomerular filtration rate has several sources of error such as tubular creatinine secretion or faulty urine collections. On the other hand Cr-51-EDTA test is reliable and accurate, except in patients with edema, in whom the radioisotope equilibrium is retarded after injection. Aim: To validate a 4-hours creatinine clearance correlating it with Cr-51-EDTA test. Methods: In 59 non insulin dependent diabetic patients without diabetic nephropathy, glomerular filtration rate was measured using one 50 mu Ca injection of Cr-51-EDTA and collecting blood samples for radioactivity measurement at 10, 30, 120 and 240 min. Simultaneously, creatinine clearance was measured using a 4 hours urine collection. Results: The general correlation coefficient between both methods was 0,85 (p<0,001). For glomerular filtration rates below 95 ml/min the correlation coefficient was 0,8 (P<0,001), for values between 95 and 127 ml/min, the correlation was 0,51 (p<0,001) and for values over 127 ml/min the correlation was 0,8 (P<0,001). The regression equation obtained was y=1,2x + 13 where y was the glomerular filtration rate measured with Cr-51-EDTA and x the same value measured with creatinine clearance. Conclusions: The four hours creatinine clearance is a reliable method to estimate glomerular filtration rate.