Changing to C.Difficile PCR Testing: The Impact on a Large Community Hospital

Background: Current guidelines recommend 2-step testing for the diagnosis of C. difficile-associated disease (CDAD). Published experience using PCR exclusively to diagnose CDAD is limited. For quality improvement purposes, our hospital switched from toxin EIA to a 2-step approach, then converted to exclusive PCR testing. We evaluated the impact of these testing changes.

Methods: Retrospective, observational study from Dec 2008-Feb 2010. Toxin EIA was used during period 1, 2-step testing was used during period 2, PCR was used during period 3. Tests for the same patient within 8 weeks were counted as the same episode. Nosocomial cases were positive tests >3 days after admission.

Results: 9,725 patients were tested for CDAD. Frequency of patients tested and demographic characteristics were similar across all time periods. Toxin EIA (period 1) identified 14.2% of CDAD cases. 2-step testing (period 2) identified 17.5% CDAD cases, and PCR (period 3) identified CDAD in 20%. CDAD incidence increased in both community-onset and nosocomial cases. The average number of tests performed per episode decreased with PCR testing. Median time from initial sample collection to first positive test result was reduced to 17 hours with PCR. Positive results were available within 12 hours 58.4% of the time with PCR. All differences were statistically significant (p<0.05).

Conclusion: PCR testing detected an additional 23.5 CDAD patients/month compared to toxin EIA, and an additional 10.3 patients/month compared to 2-step testing. PCR detected more CDAD patients with less frequent testing, and allowed for a faster diagnosis compared to toxin EIA and 2-step testing.