Determination of glomerular filtration rate (GFR) on two consecutive days using inulin in a single-sample plasma clearance method.

Reliable estimation of the GFR is essential in nephrological practice for the early recognition and follow-up of latent or residual renal disturbance. The GFR of ten healthy volunteers on two consecutive days and of 40 patients with different renal diseases were investigated by means of a plasma slope clearance technique. After injection of 5 g/50 ml inulin solution, eight plasma samples were taken at 10, 20, 30, 40, 120, 180, 240, 300 min p.i. and analyzed with the aid of a fully enzymatic method. The results were correlated on the basis of 1- and 2-compartment models (1 CM, 2 CM) and the one-sample method (1 S), using only the plasma inulin concentration of the 240 min p.i. sample. The accuracy of the GFR data of volunteers estimated in these models was checked by comparison with the standardized agewise normal values, while for the patient group we found in terms of equations of correlation: 1. GFR (2 CM) = 4.46 + 0.763*GFR (1 S), n = 31, r = 0.985 2. GFR (2 CM) = 1.27*GFR (1 CM)0.9, n = 40, r = 0.996 3. GFR (1 CM) = 0.568*(GFR[1 S] + 5.85)1.11, derived The single-sample method using inulin is closely correlated to multi-sample methods but much more suitable for patients and staff. Therefore, it is recommended for clinical use.