The importance of considering different healthcare settings when estimating the burden of Clostridium difficile.

BACKGROUND: Traditional surveillance methods may underestimate the true burden of Clostridium difficile infection (CDI) because they fail to capture cases brought to medical attention in outpatient settings or diagnosed during non-face-to-face patient-provider interactions.
METHODS: We identified CDIs diagnosed among Kaiser Permanente Northwest patients between 1 June 2005 and 30 December 2012. We categorized infections by whether they were diagnosed during an inpatient or outpatient encounter and whether they were diagnosed during a face-to-face (eg, hospitalization, outpatient visit) or non-face-to-face encounter (eg, phone, e-mail). We constructed a baseline surveillance estimate that included CDIs identified during hospitalization, representing burden captured through traditional surveillance approaches. We then constructed 2 additional estimates: 1 that included CDIs identified during outpatient face-to-face encounters and 1 that also included CDIs identified during non-face-to-face encounters.
RESULTS: We identified 8024 CDIs. Twenty-four percent occurred during a hospitalization, while the remaining CDIs were recognized in the outpatient setting. Surveillance focused on hospitalized patients would have captured less than one-quarter of total burden. The addition of cases identified during outpatient face-to-face encounters would account for 80% of CDIs. An additional 1702 CDIs would not be captured without inclusion of non-face-to-face encounters; thus, surveillance approaches that do not include telephone or e-mail encounters would miss 21% of CDIs.
CONCLUSIONS: Surveillance approaches that do not include outpatient or nontraditional encounters miss a substantial proportion of CDIs. Failure to capture these cases leads to underestimation of disease burden and difficulty in measuring interventions to control CDI.