Impact of iodine contrast media on gamma camera-based GFR and factors affecting the difference between serum creatinine-based estimated GFR and Gate's GFR

Objective We aimed to elucidate the factors underlying the difference between estimated glomerular filtration rate (eGFR) calculated from serum creatinine and Gate's GFR (gGFR) measured using technetium-99m diethylene triamine pentaacetic acid (Tc-99m-DTPA) scintigraphy. Methods This study was based on consecutive patients who underwent Tc-99m-DTPA scintigraphy at our hospital between January 2021 and December 2022 and whose blood serum creatinine data were obtained on the same day as the Tc-99m-DTPA scintigraphy. Relationships between the ratio of gGFR and eGFR (gGFR/eGFR) and age, sex, BMI, visceral fat, psoas muscle index (PMI), serum blood urea nitrogen, and creatinine level were investigated based on 75 patients. Additionally, for 44 patients who had two or more follow-up DTPA studies, we compared gGFR values for studies that used iodine contrast media (ICM) for computed tomography before same-day Tc-99m-DTPA studies and those that did not in the same patients. Results Weak correlations were observed between gGFR/eGFR and PMI (r = 0.30), BMI (r = 0.24), and the visceral fat area (r = 0.33). Multi-regression analyses showed that gGFR/eGFR was correlated with PMI (beta = 0.34, P < 0.01) and approached significance with the visceral fat area (beta = 0.24, P = 0.05). A significant difference was observed in gGFR between patients who received ICM before the Tc-99m-DTPA renogram and those who did not (P < 0.001, eGFR 80.5 +/- 19.0 vs. 91.7 +/- 27.8 ml/min). Conclusion ICM administration temporarily decreased gGFR, and increased muscle mass increased the difference between eGFR and gGFR values.