COMPARISON OF 4 LABORATORY TESTS FOR DIAGNOSIS OF CLOSTRIDIUM-DIFFICILE-ASSOCIATED DIARRHEA

Four different laboratory tests for diagnosis of Clostridium difficile -associated diarrhea were compared to determine the optimal one for ma nagement of patients with hospital-acquired diarrhea, Stool samples fr om 231 patients with diarrhea were tested by the following methods: cu lture for Clostridium difficile with subsequent determination of exoto xin production, with a toxigenic Clostridium difficile positive (TCP) result considered truly positive; enzyme immunoassay (EIA); latex aggl utination test; and an immunobinding blot assay, The rates of positive results were as follows: EIA 5.5%, TCP 7.3%, latex agglutination 16.7 %, and immunobinding blot assay 26.1%. Compared to the TCP results, th e sensitivity and specificity were, respectively, 61 and 98% for EIA, 47 and 85% for latex agglutination, and 60 and 76% for the immunobindi ng blot assay. Samples from patients with greater than or equal to 6 s tools/day were TCP and EIA positive in 27 and 17% of cases, respective ly, whereas in patients with < 6 stools/day, these percentages decreas ed to 2 and 3%, respectively (p < 0.001). In hospitalized patients wit h greater than or equal to 6 stools/day, EIA appears to be the optimal test for diagnosis of Clostridium difficile-associated diarrhea, with a 73% positive predictive value and a 97% negative predictive value, However, in patients with < 6 stools/day, the prevalence of Clostridiu m difficile is low, and laboratory detection of this organism remains problematic.