#4179 DIFFERENCES IN PROTOCOLS FOR MEASURING GLOMERULAR FILTRATION RATE USING IOHEXOL

Abstract Background and Aims When assessing kidney function, measurement of glomerular filtration rate (mGFR) using an exogenous marker such as iohexol is the gold standard. In this study, we aim to identify similarities differences between iohexol-based mGFR protocols. Method Detailed data on protocols were obtained a standardized survey sent centres in Europe US. It was completed by 15 participants. Data are reported number percentage (n, %). Results participating centres, measurements performed after referral nephrologist (n=6, 40%), other specialties (n=5, 33%) or for research purposes (n=4, 27%). Most common indications evaluation donors 33%), drug dosing 27%), abnormal body composition (n=3, 20%) transplant participants perform morning (n=10, 67%), with patients withholding caffeine fasting 27%) avoiding heavy meals 20%). use IV dose 5 mL 300 mg I/mL 67 %) based weight (n=2, 13%). The timing sample collection shown Figure 1, most often single per time point (n=12, 80%). Iohexol measured LC-MS (n=8, 53%) LC-UV (n=7, 47%). Within-assay variability ranges <2% 6-8% (n=1, 7%) between-assay 13%) asked about assumptions corrections, make one-compartment assumption their PK model 53%), others making two-compartment measurement-dependent assumptions. surface area according DuBois-formula (n=6 (40%), Haycock Schwarz formula not-specified Some correct eGFR (n=9, 60 participate external quality control (Equalis, n=12, Conclusion There large variation mGFR, which highlights need protocol before widespread clinical routine.