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

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.

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.

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.

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.