title: Accuracy of GFR estimating equations in a large Swedish cohort: implications for radiologists in daily routine and research.
abstract: Background Guidelines recommend estimation of glomerular filtration rate (eGFR) prior to iodine contrast media (CM) examinations. It is also recommended that absolute eGFR in mL/min, not commonly used relative GFR (adjusted to body surface area; mL/min/1.73 m2), should be preferred when dosing and evaluating toxicity of renally excreted drugs. Purpose To validate the absolute Lund-Malmö equation (LM-ABS) in comparison with the absolute Cockcroft-Gault (CG) equation and the relative equations, revised Lund-Malmö (LM-REV), MDRD, and CKD-EPI, after converting relative estimates to absolute values, and to analyze change in eGFR classification when absolute instead of relative eGFR was used. Material and Methods A total of 3495 plasma clearance of iohexol to measure GFR (mGFR) served as reference test. Bias, precision, and accuracy (percentage of estimates ±30% of mGFR; P30) were compared overall and after stratification for various mGFR, eGFR, age, and BMI subgroups. Results The overall P30results of CG/LM-ABS/LM-REV/MDRD/CKD-EPI were 62.8%/84.9%/83.7%/75.3%/75.6%, respectively. LM-ABS was the most stable equations across subgroups and the only equation that did not exhibit marked overestimation in underweight patients. For patients with relative eGFR 30-44 and 45-59 mL/min/1.73 m2, 36% and 58% of men, respectively, and 24% and 32% of women, respectively, will have absolute eGFR values outside these relative eGFR intervals. Conclusion Choosing one equation to estimate GFR prior to contrast medium examinations, LM-ABS may be preferable. Unless absolute instead of relative eGFR are used, systematic inaccuracies in assessment of renal function may occur in daily routine and research on CM nephrotoxicity may be flawed.
authors.affiliation: 1 Department of Translational Medicine, Division of Medical Radiology, Skåne University Hospital, Malmö, Sweden.
authors.forename: Ulf
authors.initials: U
authors.lastname: Nyman
authors.affiliation: 2 Department of Clinical Chemistry, Skåne University Hospital, Lund, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Grubb
authors.affiliation: 2 Department of Clinical Chemistry, Skåne University Hospital, Lund, Sweden.
authors.forename: Veronica
authors.initials: V
authors.lastname: Lindström
authors.affiliation: 3 R&D Centre Skåne, Skåne University Hospital, Lund, Sweden.|4 Department of Occupational and Environmental Medicine, Lund University, Lund, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Björk
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003287:Contrast Media / Q000493:pharmacokinetics*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007472:Iohexol / Q000493:pharmacokinetics*; D007677:Kidney Function Tests / Q000379:methods* / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D000072177:Radiologists; D011871:Radiology; D015203:Reproducibility of Results; D012106:Research; D013548:Sweden; D055815:Young Adult
chemical_list: D003287:Contrast Media; D007472:Iohexol
keywords: Contrast media; creatinine; glomerular filtration rate (GFR); kidney disease and kidney function tests