title: Repeat stool testing to diagnose Clostridium difficile infection using enzyme immunoassay does not increase diagnostic yield.
abstract: OBJECTIVE
  Clostridium difficile infection (CDI) is a hospital-acquired infection with increasing incidence and severity. The most frequently used test to diagnose CDI is an enzyme immunoassay (EIA) for toxins A and B in stool samples. It is common to test 2 or more stool samples, based on the assumption that this detects CDI with greater sensitivity than analysis of 1 sample. We investigated whether repeat stool testing significantly improves the diagnostic yield for CDI.
  
  
  METHODS
  We performed a retrospective analysis of hospitalized patients who were tested for CDI using EIA. From year 2005 to 2008, 39,402 stool samples from 17,971 patients with 29,373 diarrhea episodes were tested. Transition probabilities were calculated based on results from repeated tests.
  
  
  RESULTS
  A total of 2692 diarrheal episodes (9.17%) were diagnosed with CDI. Based on results of 3 consecutive tests, 2675 (99.36%) were diagnosed with CDI. The first stool sample tested produced positive results for 90.7% of cases. When samples were tested consecutively, for the second and third time, an additional 6.6% and 2% patients had positive test results, respectively. If the first test result was negative, the probability of the second test result being positive was 2.7%. If the first 2 test results were negative, the probability of the third test result being positive was 2.3%.
  
  
  CONCLUSIONS
  In patients who had multiple stool samples tested for CDI by EIA, almost 91% were accurately diagnosed based on the results of a single stool sample alone. Subsequent testing yielded a positive result in only 8.6% of patients. We therefore recommend that repeat testing not be done on a routine basis because it does not significantly improve diagnostic yield.
authors.affiliation: Department of Neurological Surgery, Neurological Institute, Cleveland Clinic, Ohio, USA. deshpaa@ccf.org
authors.forename: Abhishek
authors.initials: A
authors.lastname: Deshpande
authors.forename: Vinay
authors.initials: V
authors.lastname: Pasupuleti
authors.forename: Preethi
authors.initials: P
authors.lastname: Patel
authors.forename: Gati
authors.initials: G
authors.lastname: Ajani
authors.forename: Geraldine
authors.initials: G
authors.lastname: Hall
authors.forename: Bo
authors.initials: B
authors.lastname: Hu
authors.forename: Anil
authors.initials: A
authors.lastname: Jain
authors.forename: David D K
authors.initials: DD
authors.lastname: Rolston
mesh_terms: D000328:Adult; D000368:Aged; D001426:Bacterial Proteins / Q000032:analysis*; D001427:Bacterial Toxins / Q000032:analysis*; D019411:Clinical Laboratory Techniques / Q000379:methods*; D016360:Clostridioides difficile / Q000378:metabolism / Q000472:pathogenicity*; D003015:Clostridium Infections / Q000175:diagnosis*; D004768:Enterotoxins / Q000032:analysis*; D005243:Feces / Q000737:chemistry*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile