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

Rationale and Objectives: 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. Materials and Methods: 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. Results: 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 m² (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 m² 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 m². 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 m². Conclusions: POC eGFR testing identified a significant number of individuals with renal dysfunction not found by the pre-MR imaging questionnaire alone.