753. Comparison of C. difficile Testing Approaches at a Large Tertiary-Care Hospital
Session: Oral Abstract Session: Clostridium difficile: Detection, Transmission, and Treatment
Friday, October 21, 2011: 2:15 PM
Room: 151AB
Background: Current guidelines recommend 2-step testing over toxin EIA for the diagnosis of C. difficile-associated disease (CDAD). Published experience using PCR exclusively to diagnose CDAD is limited. For quality improvement purposes, our 900-bed tertiary care community hospital switched from toxin EIA to a 2-step approach (confirmatory PCR if positive screening glutamate dehydrogenase EIA). 6 months later we converted to exclusive PCR testing. We evaluated the impact of these testing changes.

Methods: Retrospective, observational study. Toxin EIA was used during period 1 (Dec 2008-Nov 2009); 2-step testing was used during period 2 (Dec 2009-May 2010); PCR was used during period 3 (May 2009-Feb 2010). Repeat C. difficile tests for the same patient within 8 weeks were attributed to the same episode. Nosocomial cases were defined as those with a positive test >3 days after admission.

Results: An average of 354.5 patients/month were tested for CDAD (total 9,725 unique episodes); frequency of unique patients tested and basic demographic data was similar across all time periods. Toxin EIA (period 1) identified CDAD in 14.2% of patients. 2-step testing (period 2) identified CDAD in 17.5% of patients, and PCR (period 3) identified CDAD in 20.0%. This increased CDAD incidence was seen in both community-onset and nosocomial cases. The average number of tests performed per episode decreased from 2.70 with toxin EIA to 2.30 with 2-step testing, and to 1.39 with PCR. Median time from initial sample collection to first positive test result was 32.3 hours with toxin EIA, 26.5 hours with 2-step testing, and 17.0 hours with PCR. Positive results were available within 12 hours of the initial test 20.3% of the time with toxin EIA, 17.0% with 2-step testing, and 58.4% of the time with PCR. All differences between periods described above were statistically significant (p<0.05).

Conclusion: At our 900-bed hospital, 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.

Subject Category: D. Diagnostic microbiology

Jonathan Grein, MD1, Margaret Ochner, MD2, Angela Jin, MPH1, Ha Hoang, MPH1, Margie Morgan, PhD3 and Rehka Murthy, MD1, (1)Hospital Epidemiology, Cedars-Sinai Medical Center, Los Angeles, CA, (2)Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, (3)Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA


J. Grein, None

M. Ochner, None

A. Jin, None

H. Hoang, None

M. Morgan, None

R. Murthy, None

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