Development and Validation of a Risk Score for Clostridium difficile Infection in Medicare Beneficiaries: A Population-Based Cohort Study

ObjectivesTo create a risk stratification score for Clostridium difficile infection (CDI) in elderly adults. DesignA sample from the Medicare 5% data set linked to Medicaid and Minimum Data Set (MDS) files from 2008 to 2009. Risk score was derived via a split-cohort through logistic regression model used to assign numerical values to each retained covariate. Score characteristics were tested using a threshold analysis. SettingCommunity, long-term, and acute care settings. ParticipantsPopulation-based sample Medicare beneficiaries aged 65 and older on January 1, 2008, with continuous Medicare coverage from January 1, 2008, through December 31, 2009. MeasurementsThe primary outcome was incident CDI, defined as International Classification of Diseases, Ninth Revision, Clinical Modification code 008.45 or CDI according to the MDS, and no CDI in the preceding 12 months. ResultsThe cohort consisted of 6,838 participants with CDI and 1,158,327 without. Logistic regression modeling (hospitalization, nursing home stay, or antibiotics in prior year; inflammatory bowel, chronic liver, chronic kidney, or cardiac disease; aged 75, Northeast residence; c-statistic = 0.858) was used to determine to a score out of 22 possible points. A score of seven points (found in 18.8% of the total population) had a negative predictive value of 98.7%. ConclusionCDI risk is high and age dependent in the population aged 65 and older. By stratifying risk, this score should help ensure efficient allocation of prevention resources.