Table 2.

Classification of CDI Cases by Setting of Acquisition

Case definition	Criteria for classification
CO-CDI	- Discharge code ICD-9-CM 008.45 as Primary diagnosis
HO-CDI	- Discharge code ICD-9-CM 008.45 as secondary diagnosis, without a primary diagnosis of a CDI-related symptom (e.g. diarrhea) - Study population ≥ 48 h of hospitalization - Symptom onset and/or positive laboratory assay at least ≥ 48 h hospitalization
Both CDI	- No distinction of settings of acquisition - Discharge code ICD-9-CM 008.45 in any position

Abbreviations: CO-CDI community-onset CDI, HO-CDI hospital-onset CDI, ICD-9-CM The International Classification of Diseases, Ninth Revision, Clinical Modification