Overreporting healthcare-associated C. difficile: A comparison of NHSN LabID with clinical surveillance definitions in the era of molecular testing.

Background: Clostridium difficile infection (CDI) is the most common healthcare-associated gastrointestinal infection. Hospitals are required to report cases of healthcare facility-onset CDI (HO-CDI) using the National Healthcare Safety Network's CDI laboratory-identified (LabID) event definition. The aim of this study was to determine the extent of potential over-reporting due to the exclusion of important clinical data within LabID reporting definitions.

Methods: In 2015, retrospective chart review was performed on 212 HO-CDI cases reported from a large urban medical center. Cases had positive polymerase chain reaction test for the C. difficile toxin B gene from an unformed stool specimen collected >3 days after admission and >8 weeks after most recent LabID event. Cases were categorized into "clinical surveillance" groups: community-acquired infection, recurrence/relapse, asymptomatic colonization, colonization with self-limited symptoms, possible HO-CDI, and probable HO-CDI.

Results: Of the infections, 13.6% were community acquired, 2.8% were recurrent/relapse, 1.9% were asymptomatic colonization, 18.4% were symptomatic colonization, 38.7% were possible HO-CDI, and 24.5% were probable HO-CDI. Within 24 hours of testing, 34.1% of patients had received a stool softener and/or laxative.

Conclusions: Laxative use and failure to identify community-onset infection may contribute to misclassification of HO-CDI. Only 62% of reported cases met clinical surveillance criteria.