A Clostridium difficile infection "intervention": Change in toxin assay results in fewer C difficile infection cases without changes in patient outcomes

Background: Clostridium difficile infection (CDI) is most commonly diagnosed using toxin enzyme immunoassays (EIAs). A sudden decrease in CDI incidence was noted after a change in the EIA used at Barnes-Jewish Hospital in St Louis. The objective of this study was to determine whether the decreased CDI incidence related to the change in EIA resulted in adverse patient outcomes. Methods: Electronic hospital databases were used to collect data on demographics, outcomes, and treatment of inpatients who had a C difficile toxin assay performed between January 4, 2009, and April 3, 2009 (period A, preassay change) and between May 21, 2009, and August 17, 2009 (period B, postassay change). Results: Assays were positive in 240 of 1,221 patients (19.7%) during period A and in 106 of 1160 patients (9.1%) during period B (P <.01). There was no difference in mortality or discharge to hospice between the 2 periods (10.3% vs 10.1%; P =.90). Patients tested in period B were less likely to receive metronidazole or oral vancomycin (P <.01). Conclusions: The new EIA resulted in fewer positive tests and reduced anti-CDI therapy. There was no difference in mortality between the 2 periods, suggesting that the decreased incidence was due to increased assay specificity, not decreased sensitivity.