Infection Control & Hospital Epidemiology

Original Articles

High Proportion of False-Positive Clostridium difficile Enzyme Immunoassays for Toxin A and B in Pediatric Patients

Philip Toltzisa1 c1, Michelle M. Nerandzica2, Elie Saadea2, Mary Ann O'Riordana1, Sarah Smathersa3, Theoklis Zaoutisa3, Jason Kima3 and Curtis J. Donskeya4

a1 Rainbow Babies and Children's Hospital, Cleveland, Ohio

a2 Research Service, Cleveland VA Medical Center, Cleveland, Ohio

a3 Children's Hospital of Philadelphia, Philadelphia, Pennsylvania

a4 Geriatric Research, Education and Clinical Center, Cleveland, Ohio

Abstract

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.

Infect Control Hosp Epidemiol 2012;33(2):175-179

(Received July 01 2011)

(Accepted September 22 2011)

Correspondence

c1 Division of Pharmacology and Critical Care, Rainbow Babies and Children's Hospital, 11100 Euclid Avenue, Cleveland, OH 44106 (pxt2@case.edu)