In-vivo radionuclide GFR correlates poorly with eGFR measured from creatinine based equations

Objectives To compare the values of glomerular filtration rate (GFR) calculated using in-vivo radionuclide technique from 99mTc-DTPA scintigraphy (Gate’s method) and eGFR values based on serum creatinine equations (CKD-EPI & MDRD equations)

Methods Retrospective analysis of 36 patients (12 females, 24 males), median age 37.5 year (range: 18-70). All patients underwent gamma camera (GC) based diuretic renogram using 99mTc-DTPA. Gate’s method was employed to calculate in-vivo GFR. Region of interest (ROI) was drawn around the whole kidney including the renal pelvis. The background was placed on different sites: sub-renal rectangle (Bkg1), inferolateral semilunar ROI (Bkg2) and peri-renal (Bkg3). All patients had normal serum creatinine according to recent assay in the same laboratory within 1 month from the radionuclide study

Results Mean serum creatinine was 1.1 (± 0.2) mg%. Mean eGFR based on CKD-EPI equation was 82.6 (± 20.4) ml/min/1.73 m². Mean eGFR based on MDRD equation was 74.6 (± 20.4) ml/min./1.73 m² They were highly correlated (R = 0.975; P < 0.0001). The measured GC in-vivo GFR using Bkg1, Bkg2 & Bkg3 were 73.6 (± 25.4), 73.3 (±24.5) and 43.9 (± 20.8) ml/min/1.73 m². All of them show poor correlation with CKD-EPI and MDRD equations (Table).

Conclusions In-vivo GFR using 99mTc-DTPA dynamic renal scintigraphy correlates poorly with the bedside eGFR equations based on serum creatinine (CKD-EPI and MDRD).