THE LACK OF VALUE OF REPEATED CLOSTRIDIUM-DIFFICILE CYTOTOXICITY ASSAYS

Objective.-To determine the value of repeated Clostridium difficile cy totoxicity assays (CA). Design.-AII CAs performed during 1993 were ret rospectively reviewed and correlated with clinical data. Assays were g rouped into episodes, which were defined as one or more successive tes ts performed on a single patient within 7 days or less of each other. Setting.-A 751-bed tertiary care facility. Patients.-AII patients with ;Clostridium difficile CAs submitted to the microbiology laboratory. R esults.-There were 947 episodes with two or more CAs. In 15 of these e pisodes, a negative CA result was followed by a positive result, and i n 25 cases, a positive result was followed by a negative one. We revie wed the clinical data for these cases. Of the 947 episodes with two or more CAs, the repeated assays provided new information that was used in patient care in fewer than nine cases. Repeated testing within 7 da ys of an initial CA accounted for 36% of all assays performed, but pro vided clinically useful information in only about 1% of cases. Conclus ions.-Clostridium difficile CAs should not be repeated within a 7-day period.