Correlación entre clearence de creatinina de 4 horas y la prueba de Cr-EDTA / Correlation between 4 hours creatinine clearence and Cr-EDTA test

RESUMEN

Creatinine clearence 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 51Cr-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 clearence correlating it with 51Cr-EDTA test. Methods: In 59 non insulin dependent diabetic patients without diabetic nephropathy, glomerular filtration rate was measured using one 50 µCi injection of 51Cr-EDTA and collecting blood samples for radioactivity measurement at 10, 30, 120 and 240 min. Simultaneously, creatinine clearence 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 51Cr-EDTA and x the same value measured with creatinine clearence. Conclusions: The four hours creatinine clearence is a reliable method to estimate glomerular filtration rate