A Quick C. difficile Infection “Intervention”: Change in Toxin Assay Results in Lower Number of CDI Cases with No Changes in Patient Outcomes

Background: Clostridium difficile infection (CDI) is most commonly diagnosed with use of a toxin EIA.  The sensitivity and specificity of toxin EIAs vary. A sudden decrease in CDI incidence was noted with change in toxin assays at Barnes-Jewish Hospital (BJH) in St. Louis, MO.  We investigated the impact this change had on patient outcomes.

Objective: To determine if a decrease in CDI incidence related to a change in toxin EIA resulted in adverse patient outcomes.

Methods: Retrospective cohort of patients tested for CDI at BJH. Electronic hospital databases was used to collect data on demographics, outcomes and treatment information of inpatients with at least one C. difficile toxin assay performed between 1/4/09 and 4/3/09 (period A, Remel ProspectT CDIF) and 5/21/09 and 8/17/09 (Period B, Techlab C. DIFFICLE TOX A/B).  Analyses included logistic regression and Mann-Whitney U tests in SPSS 16.0 (SPSS Inc, Chicago, IL).

Results: During period A, of 1221 patients with ≥1 toxin assay performed, 240 (19.7%) were positive on the first test.  During period B, 106 (9.1%) of 1160 patients were positive on the first test (p<0.01).  995 (49%) of the 2035 patients who were negative on the first test had ≥1 additional test performed; 102 (21.6%) became positive on a subsequent test during period A, compared with 20 (3.8%) during period B (p<0.01).  Of the patients with >1 toxin assay ordered during their admission, the median number of tests ordered until the patient had a positive toxin assay or was discharged did not differ between the time periods (median=2 for both groups, p=0.74).  Patients who had CDI testing in period A were more likely to be discharged to long term care (3.7% in period A vs 2.1% in period B, p=0.03) but had no difference in mortality or discharge to hospice (10.3% vs 10.1%, p=0.90).  Patients tested in period B were less likely to receive metronidazole (Odds ratio (OR) 0.79, 95% Confidence Interval (CI) 0.67-0.93) or oral vancomycin (OR 0.44, 95% CI 0.34-0.58) after the first toxin assay was sent, and less likely to receive anti-diarrheals after the first toxin assay was sent (OR 1.32, 95% CI 1.09, 1.59).

Conclusions: A new C. difficile toxin assay resulted in fewer positive tests and reduced anti-CDI therapy among patients with >1 test performed.  There was no difference in mortality between the two periods.