Evaluation of the clinical usefulness of C-difficile toxin testing in hospitalized patients with diarrhea

Although numerous studies have evaluated the sensitivity and specificity of different assays for Clostridium difficile toxin, none has evaluated how p hysicians utilize these tests or respond to test results. Therefore, we ass essed patient characteristics, clinical findings, and physician responses t o positive and negative assay results at two university-affiliate hospitals , one of which used a cell cytotoxicity assay to test for C. difficile toxi n and the other of which used an enzyme immunoassay. Two hundred one patien t samples at Hospital A and 199 samples at Hospital B were assessed. Positi ve toxin assays were more frequent at Hospital A than at Hospital B (p < 0. 001), at least in part due to the fact that patients tested at Hospital A w ere more likely to have fever (p < 0.001), an abnormal abdominal exam (p < 0.001), an abnormal leukocyte count (p < 0.001), and a history of prior ant ibiotic use (p < 0.001). Empiric therapy for C. difficile before results of the toxin assay was more common (p < 0.001) at Hospital A (83/01, 41.3%) t han at Hospital B (25/199, 12.5%). Once empiric therapy was started, most p hysicians continued therapy despite negative test results (Hospital A, 76%; Hospital B, 69%). Patients who were treated empirically were more likely t han patients not treated empirically to have positive toxin assay results a nd to have fever (p < 0.001), an abnormal abdominal exam (p = 0.003), or an abnormal leukocyte count (p < 0.05). Physicians seldom ordered repeat toxi n assays (Hospital A, 14%; Hospital B, 10%) if the initial assay result was negative. In logistic regression analysis, predictors of a positive toxin assay were prior antibiotic therapy, an abnormal abdominal exam, residence at Hospital A, and age greater than or equal to 60 years. Predictors of emp iric therapy were residence at Hospital A and prior antibiotic therapy. Bec ause physicians electing to empirically treat inpatients with diarrhea rare ly alter therapy based on C. difficile toxin assay results, a more cost-eff ective management strategy may be not to obtain a toxin assay at all in suc h situations. Testing should be limited to patients who have received antib iotics within the prior month and who have significant diarrhea and/or abdo minal pain. (C) 2000 Elsevier Science Inc. All rights reserved.