High proportion of false-positive Clostridium difficile enzyme immunoassays for toxin A and B in pediatric patients.

TitleHigh proportion of false-positive Clostridium difficile enzyme immunoassays for toxin A and B in pediatric patients.
Publication TypeJournal Article
Year of Publication2012
AuthorsToltzis P, Nerandzic MM, Saade E, O'Riordan MAnn, Smathers S, Zaoutis TE, Kim J, Donskey CJ
JournalInfect Control Hosp Epidemiol
Date Published2012 Feb
KeywordsBacterial Proteins, Bacterial Toxins, Case-Control Studies, Child, Preschool, Clostridium difficile, Clostridium Infections, DNA, Bacterial, Enterotoxins, Enzyme-Linked Immunosorbent Assay, False Positive Reactions, Hospitals, Pediatric, Humans, Infant, Polymerase Chain Reaction, Predictive Value of Tests, Prospective Studies

OBJECTIVES: To determine the frequency of false-positive Clostridium difficile toxin enzyme immunoassay (EIA) results in hospitalized children and to examine potential reasons for this false positivity.

DESIGN: Nested case-control.

SETTING: Two tertiary care pediatric hospitals.

METHODS: As part of a natural history study, prospectively collected EIA-positive stools were cultured for toxigenic C. difficile, and characteristics of children with false-positive and true-positive EIA results were compared. EIA-positive/culture-negative samples were recultured after dilution and enrichment steps, were evaluated for presence of the tcdB gene by polymerase chain reaction (PCR), and were further cultured for Clostridium sordellii, a cause of false-positive EIA toxin assays.

RESULTS: Of 112 EIA-positive stools cultured, 72 grew toxigenic C. difficile and 40 did not, indicating a positive predictive value of 64% in this population. The estimated prevalence of C. difficile infection (CDI) in the study sites among children tested for this pathogen was 5%-7%. Children with false-positive EIA results were significantly younger than those with true-positive tests but did not differ in other characteristics. No false-positive specimens yielded C. difficile when cultured after enrichment or serial dilution, 1 specimen was positive for tcdB by PCR, and none grew C. sordellii.

CONCLUSIONS: Approximately one-third of EIA tests used to evaluate pediatric inpatients for CDI were falsely positive. This finding was likely due to the low prevalence of CDI in pediatric hospitals, which diminishes the test's positive predictive value. These data raise concerns about the use of EIA assays to diagnosis CDI in children.

Alternate JournalInfect Control Hosp Epidemiol
PubMed ID22227987