ESTIMATION OF THE GLOMERULAR-FILTRATION RATE IN NIDDM PATIENTS FROM PLASMA CREATININE CONCENTRATION AFTER CIMETIDINE ADMINISTRATION

OBJECTIVE - Glomerular filtration rate (GFR) can be estimated in patie nts with renal disease from plasma creatinine concentration, age, sex, and body weight according to the formula of Cockcroft and Gault. The hypothesis that this method can be improved when tubular secretion of creatinine is inhibited by cimetidine was studied in NIDDM patients. R ESEARCH DESIGN AND METHODS - In 30 outpatients with NIDDM and normo- ( n = 10). micro- (n = 9), or macroalbuminuria (n = 11), GFR was measure d as the urinary clearance during continuous infusion of I-125-labeled iothalamate. Plasma creatinine concentration was analyzed with an enz ymatic assay before and after 800 mg t.i.d. oral cimetidine was given during a 24-h period. RESULTS - Plasma creatinine rose in all patients after cimetidine administration and, as a consequence, the clearance calculated with the Cockcroft-Gault formula fell. The ratio of this fo rmula and GFR decreased from 1.16 +/- 0.20 to 0.97 +/- 0.16 (means +/- SD). This ratio tended to be smaller in the normo- (0.93) than in the micro- (0.98) and macroalbuminuric (1.00) groups. Also, 20 patients w ith a BMI <30 kg/m(2) had a smaller-ratio than those with a BMI >30 kg /m(2) (0.92 vs. 1.07; P < 0.05). Bland and Airman analysis showed a di fference of the Cockcroft-Gault formula and GFR of 12.0 +/- 17.4 ml . min(-1).(1.73 m(2))(-1), which decreased to -3.8 14.8 ml . min(-1).(1. 73 m(2))(-1). The same analysis of 24-h creatinine clearance with urin e collection and GFR showed larger standard deviations. CONCLUSIONS - GFR can be estimated in an acceptable way from plasma creatinine conce ntration after cimetidine administration in outpatients with NIDDM. De spite a nonsignificant underestimation in normoalbuminuric and overest imation in overweighted patients, this method is superior to 24-h crea tinine clearance with outpatient urine collection.