Glomerular filtration rate estimated from the uptake phase of 99mTc-DTPA renography in chronic renal failure

Abstract

Background, The purpose of the study was to compare the estimation of glomerular filtration rate (GFR) from 99mTc-DTPA renography with that estimated from the renal clearance of 51Cr-EDTA, creatinine and urea. Methods. Fifty patients with reduced renal function (serum creatinine between 150 and 600 μmol/l) were enrolled in the study. GFR was estimated from the uptake phase of 99mTc-DTPA renography (GFR(DTPA)). The renal clearance of 51Cr-EDTA (GFR(EDTA)) was used as the reference method. Creatinine clearance (C(Cr)), urea clearance (C(Ur)) and the mean of urea and creatinine clearance (C((Cr + Ur)/2)) were also calculated from urine collected during a period of 24 h. Limits of agreement were used for method comparison. Results. The limit of agreement between GFR(DTPA) and GFR(EDTA) was 2 ± 17 ml/min. The mean difference did not deviate significantly from zero. The other clearance techniques had larger limits of agreement and a mean difference significantly different from zero. Furthermore, C(Ur) and C((Cr + Ur)/2) had systematic deviations of the differences, indicating that C(Ur) and C((Cr + Ur)/2) are poor estimates of GFR. Conclusion. The limit of agreement between GFR(DTPA) and GFR(EDTA) are acceptable and, therefore, GFR estimated from (99M)Tc-DTPA renography is acceptable for clinical use in patients with reduced renal function. Furthermore, the method is simple and less time consuming compared with renal clearance techniques.