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183 The effect of PCR diagnosis on Clostridium difficile infection rates

Saturday, April 2, 2011
Trinity Ballroom (Hilton Anatole)
Jose Cadena, MD , South Texas Veterans Health Care System and University of Texas Health Science Center, San Antonio, TX
Patti Grota, RN, PhD , South Texas Veterans Health Care System, San Antonio, TX
Christopher R. Frei, Pharm, D , The University of Texas at Austin and The University of Texas Health Science Center at San Antonio, San Antonio, TX
Jan E. Patterson, MD , South Texas Veterans Healthcare System, University of Texas Health Science Center at San Antonio, San Antonio, TX
Background:  This VA facility implemented PCR testing for Clostridium difficile in stool in February 2010. The single PCR test (Cephed Xpert C difficile assay, Sunnyvale CA) is more sensitive (97%) than the former method of EIA (ProSpecT C. difficile Toxin A/B Microplate Assay; Remel, Lenexa, Kansas) in triplicate (70%). We anticipated a transient increase in C. difficile associated infection (CDI) cases due to better identification with PCR, followed by a subsequent decrease in cases due to more rapid and complete infection control for our CDI population.

Objective: To compare CDI incidence and diagnostic costs before and after implementation of a PCR diagnostic test.

Methods:   All acute and intensive care units were included in this analysis. CDI cases were defined according to standardized definitions from the CDC.  Group 1 included CDI cases identified by triplicate EIA between October 1, 2009 and February 28, 2010. Group 2 included CDI cases identified by single PCR between March 1, 2010 and September 30, 2010. PASW Statistics version 18 Quality Control Charts were used to quantify and compare CDI cases. CDI rates were reported as number of cases per 1000 patients per month. Mean monthly CDI rates in the pre-and post-implementation periods were compared by chi-square. Mean diagnostic costs were compared by StudentÕs t-test.

Results: After the implementation of PCR testing for CDI, the rates of infection increased to 2.4 per 1000 pt days, followed by steadily decline over the following months. Overall, CDI rates post implementation were significantly lower than pre implementation rates: CDI rates in pre-implementation period was 3/1000 pts per month (EIA, n=143, M=3.0, SD= 4.22) and 0.74 pts per 1000 pts per month in time period 2 (PCR, n=49, M=. 74. SD 1.43); t=3.6, p=<0.01.

Conclusions: CDI rates decreased significantly after implementation of a PCR diagnostic test. The increased sensitivity of the PCR testing with one test likely led to more rapid diagnosis and treatment of affected patients, effectively preventing spread of CDI to other patients.