[Correlation between four-hour creatinine clearance and 51Cr-EDTA test].

BACKGROUND

Creatinine 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 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 clearance 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 microCi injection of 51Cr-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 51Cr-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.