Reporting Catheter-Associated Urinary Tract Infections: Denominator Matters

OBJECTIVE: To evaluate two different methods of measuring catheter-associated urinary tract infection (CAUTI) rates in the setting of a quality improvement initiative aimed at reducing device utilization. DESIGN, SETTING, AND PATIENTS: Comparison of CAUTI measurements in the context of a before-after trial of acute care adult admissions to a multicentered healthcare system. METHODS: CAUTIs were identified with an automated surveillance system, and device-days were measured through an electronic health record. Traditional surveillance measures of CAUTI rates per 1,000 device-days (R1) were compared with CAUTI rates per 10,000 patient-days (R2) before (T1) and after (T2) an intervention aimed at reducing catheter utilization. RESULTS: The device-utilization ratio declined from 0.36 to 0.28 between T1 and T2 (P = .001), while infection rates were significantly lower when measured by R2 (28.2 vs 23.2, P = .02). When measured by R1, however, infection rates trended upward by 6% (7.79 vs. 8.28, P = .47), and at the nursing unit level, reduction in device utilization was significantly associated with increases in infection rate. CONCLUSIONS: The widely accepted practice of using device-days as a method of risk adjustment to calculate device-associated infection rates may mask the impact of a successful quality improvement program and reward programs not actively engaged in reducing device usage.