CREATININE CLEARANCE CAN BE PREDICTED FROM PLASMA CREATININE AND BODY-COMPOSITION ANALYSIS BY MEANS OF ELECTRICAL BIOIMPEDANCE

The aim of this study was to evaluate the possibility of predicting cr eatinine clearance (C-Cr) from plasma creatinine (P-Cr) and body com-p osition analysis by means of electrical impedance, thereby avoiding ur ine collection. Fat-free mass (FFM) and body cell mass (BCM) were meas ured in 50 renal patients (M29, F21; aged 17-74 years; mean 52.6) with different degrees of renal function (P-Cr 0.8-9.0 mg/dL, mean 2.13) b y using a tetrapolar impedance plethysmograph. The relationship betwee n 24 h urinary creatinine excretion (U-Cr) and FFM and BCM was evaluat ed in 20 of the above reported patients (MI I, F9; Pcr 08-9.0 mg/dL, m ean 2.27). The mean ratio of 24 h U-Cr/FFM was 25.6 mg/kg in males and 22.5 in females and that of 24 h U-Cr/BCM was 51.9 mg/kg in males and 48.1 in, females. C-Cr was estimated in the remaining 30 patients (M1 8, F12; P-Cr, 0.9-8.8 mg/dL mean 2.04) from individual FFM and BCM val ues and P-Cr. In the same patients C-Cr was predicted also according t o the Cockcroft and Gault formula and, for comparison, was measured wi th the conventional method by collecting 24 h urine. C-Cr predicted fr om the values of FFM and BCM gave a good estimate of 24h C-Cr more pre cise than that of Cockcroft and Gault C-Cr. Also, the repeatability of the predicted C-Cr was clearly better than that of 24 h C-Cr. In conc lusion, creatinine clearance can be predicted, avoiding urine collecti on, from plasma creatinine and body composition analysis by means of e lectrical impedance.