Efficacy of endogenous creatinine clearance in diabetic patients

One, 3 and 4-hr creatinine clearance was determined in 47 insulin dependent (type 1) diabetics where urinary creatinine was assayed after spontaneous voiding. These values were compared with calculations of total plasma clearance of 51Chromium-EDTA performed simultaneously which was regarded as a reference method for estimation of GFR. The 1 and 4-hr creatinine clearance showed a weak correlation (p less than 0.01, r = 0.44; p less than 0.01, r = 0.39) to GFR whereas the 3-hr clearance values were not found to be significantly correlated if a kinetic Jaffé reaction was used for determination of creatinine concentrations. If a more specific enzymatic method for creatinine determinations was used all three clearance values showed a correlation to GRF (p less than 0.01) indicating that non-creatinine compounds (e.g., ketone bodies) may interfere in the creatinine assay. None of the methods for determination of clearance however, predicted the GFR determined by the reference method. The serum creatinine concentrations showed a significant negative correlation (p less than 0.001, r values 0.78-0.82) to GFR but was not a reliable indicator of slightly reduced kidney function. The results imply that endogenous creatinine clearance in diabetic subjects is not a sensitive index of GFR. Further, creatinine clearance gives little additional information to that given by S-creatinine concentrations.