title: The lack of value of repeated Clostridium difficile cytotoxicity assays.
abstract: OBJECTIVE
  To determine the value of repeated Clostridium difficile cytotoxicity assays (CA).
  
  
  METHODS
  All CAs performed during 1993 were retrospectively reviewed and correlated with clinical data. Assays were grouped into episodes, which were defined as one or more successive tests performed on a single patient within 7 days or less of each other.
  
  
  METHODS
  A 751-bed tertiary care facility.
  
  
  METHODS
  All patients with Clostridium difficile CAs submitted to the microbiology laboratory.
  
  
  RESULTS
  There were 947 episodes with two or more CAs. In 15 of these episodes, a negative CA result was followed by a positive result, and in 25 cases, a positive result was followed by a negative one. We reviewed 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 days of an initial CA accounted for 36% of all assays performed, but provided clinically useful information in only about 1% of cases.
  
  
  CONCLUSIONS
  Clostridium difficile CAs should not be repeated within a 7-day period.
authors.affiliation: Department of Pathology, Brigham and Women's Hospital, Boston, Mass., USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Renshaw
authors.forename: J M
authors.initials: JM
authors.lastname: Stelling
authors.forename: M H
authors.initials: MH
authors.lastname: Doolittle
mesh_terms: D001427:Bacterial Toxins / Q000633:toxicity; D001431:Bacteriological Techniques / Q000592:standards; D002478:Cells, Cultured; D016360:Clostridioides difficile; D003967:Diarrhea / Q000382:microbiology; D004761:Enterocolitis, Pseudomembranous / Q000175:diagnosis*; D004768:Enterotoxins / Q000633:toxicity*; D006801:Humans; D008168:Lung / Q000187:drug effects / Q000196:embryology; D012008:Recurrence; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile