Single-blood-sample method for the determination of glomerular filtration rate using 99mTc-DTPA in Japanese

The study was aimed to evaluate glomerular filtration rate with 99mTc-DTPA by means of a single-plasma-sample method in Japanese. Three were 50 patients (29 males and 21 females, age range being 25 to 91 years) with diabetes mellitus of various degree of the renal function. 99mTc-DTPA of 300 MBq/2 ml that was prepared in our hospital was injected. Dynamic renal scintigraphy was carried out and 10 blood samples were taken after the injection. Blood clearance (true GFR) of 99mTc-DTPA was determined from plasma concentration which was fitted to the biexponential curve by a non-linear least squares method. Plasma concentration (ml/min/1.73 m2) after 75 min-post injection showed very higher linear regression and linear correlation with true GFR than 0.900. The best linear regression and linear correlation was observed with 180 min-sample (r = 0.989). As general, the following equation was obtained; Y = A + Bln(X), A = 436.1217 - 3.45817t + 0.01205t2 - 0.000015t3, B = -212.601 + 1.42518t - 0.04834t2 + 0.0000062t3, X = plasma concentration at sampling time t (%ID/L/1.73 m2), t = sampling time from 75 to 300 min (r > 0.900). This is the new equation of single-plasma-sample method for the determination of GFR using 99mTc-DTPA for Japanese. The clinical feasibility should be accessed in a field of a nuclear medicine practice.