Does Timing Matter?: Comparing Rates of Clostridium difficile Colonization Among Community Onset and Hospital Onset Inpatients

Background: The incidence of both community and healthcare onset Clostridium difficile infections (CDI) have increased dramatically over recent years. This surge has been associated with a rise in both community and nosocomial asymptomatic C. difficile carriage. This colonization does not currently require treatment or contact isolation, so it does not need to be identified in hospitalized patients. The aim of this study was to better understand when C. difficile testing is sent appropriately by comparing the rates of C. difficilepositive assays that represent colonization in healthcare onset (HO) versus community onset (CO) cases.

Methods: A retrospective cohort study was conducted of all patients at Mount Sinai Beth Israel who tested positive for C. difficilein 2015. In accordance with CDC guidelines, samples sent on day 3 or earlier of admission were considered CO and those sent on or after day 4 were considered HO. Chart review was done to determine the primary outcome: colonization, which is defined as a positive C. difficile assay without symptoms consistent with CDI.

Results: Fifty-four percent of the 175 patients with C. difficile positive assays were CO. There was no evidence of a relationship between timing of stool sample collection and colonization, with colonization rates of 35.8% in HO patients and 31.9% in CO patients (RR 1.12; 95% CI 0.74 – 1.79; p=0.59). Subset analysis comparing colonization in community onset patients who had healthcare exposure within 4 weeks (36.8% colonization) versus community onset without recent healthcare exposure (28.6% colonization) also showed no difference in rates (RR 1.30; 95% CI 0.72 – 2.32; p=0.40). However, among patients who were colonized with C. difficile, HO cases were 30% more likely to receive CDI treatment (OR 1.32; 95% CI 1.05 – 1.65; p=0.01).

Conclusion: In our study, there was no detectable relationship between rates of colonization and healthcare exposure. However, C. difficile colonized HO patients were more likely to be given treatment for infection compared to their colonized CO counterparts, indicating that HO colonized patients were more likely to be misdiagnosed as true infections.