Comparison of the Sensitivity of a Pre-MRI Questionnaire and Point of Care eGFR Testing for Detection of Impaired Renal Function

Abstract

The Food and Drug Administration recommends renal function estimation using laboratory testing for patients at risk for chronically reduced kidney function before the administration of gadolinium-based contrast agents (GBCAs). Point-of-care (POC) estimated glomerular filtration rate (eGFR) testing was added to the pre-magnetic resonance (MR) questionnaire at our institution in June 2008 for all patients undergoing a contrast-enhanced MR exam. This study was done to evaluate the effectiveness of a pre-MR screening questionnaire about kidney disease and to assess POC eGFR detection of additional patients at risk for nephrogenic systemic fibrosis. This retrospective study was approved by our institutional review board and determined to be Health Insurance Portability and Accountability Act compliant. Medical records, laboratory data, and pre-MR questionnaires of all patients who presented for contrast-enhanced MR scans during October 2008 were reviewed. The National Kidney Disease Education Program isotope-dilution mass spectrometry-traceable Modification of Diet in Renal Disease equation was used to calculate eGFRs using the POC creatinine laboratory value, age, race, and gender. Sensitivity and specificity were calculated using 2 × 2 tables, and 95% confidence intervals were calculated with exact binomial confidence intervals. A total of 1167 individuals presented for contrast-enhanced MR scans. Of 13 individuals on dialysis, 2 did not report renal disease. Of 1154 individuals not on dialysis, 25 had an eGFR <30 mL/min/1.73 m(2) (95% CI 1.41%-3.18%). Of these 25, 13 did and 12 did not report renal disease. The sensitivity of the questionnaire for identifying patients with an eGFR <30 mL/min/1.73 m(2) was 63.2%. POC eGFR estimations identified a prevalence of 2.17% (95% CI: 1.41%-3.18%) of the total individuals not on dialysis, with an eGFR <30 mL/min/1.73 m(2). Patients who denied kidney dysfunction had a 1.08% (95% CI: 0.56%-1.88%) posttest probability of having an eGFR <30 mL/min/1.73 m(2). POC eGFR testing identified a significant number of individuals with renal dysfunction not found by the pre-MR imaging questionnaire alone.