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 creatinine clearance (C-Cr) from plasma creatinine (P-Cr) and body com-position analysis by means of electrical impedance, thereby avoiding urine collection. Fat-free mass (FFM) and body cell mass (BCM) were measured 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) by using a tetrapolar impedance plethysmograph. The relationship between 24 h urinary creatinine excretion (U-Cr) and FFM and BCM was evaluated in 20 of the above reported patients (MI I, F9; Pcr 08-9.0 mg/dL, mean 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 (M18, F12; P-Cr, 0.9-8.8 mg/dL mean 2.04) from individual FFM and BCM values and P-Cr. In the same patients C-Cr was predicted also according to the Cockcroft and Gault formula and, for comparison, was measured with the conventional method by collecting 24 h urine. C-Cr predicted from the values of FFM and BCM gave a good estimate of 24h C-Cr more precise 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 conclusion, creatinine clearance can be predicted, avoiding urine collection, from plasma creatinine and body composition analysis by means of electrical impedance.