Background:C. difficile is the leading healthcare-associated pathogen. The C. difficile real-time polymerase chain reaction (PCR) stool test, used by >70% of hospitals, is highly sensitive but cannot differentiate colonization from infection. Inappropriate C. difficile testing may result in overdiagnosis and unnecessary treatment. Healthcare costs attributed to C. difficile are substantial, but the economic burden associated with C. difficile false positives in colonized patients is poorly understood. C. difficile PCR cycle threshold (CT) is as an inverse proxy for organism burden; high CT (≥30.9) has a high (>98%) negative predictive value compared to the reference gold standard, thus is a marker of colonization. Conversely, a low CT (≤28.0) suggests high organism burden and high specificity for true infection. Methods: A propensity score matching model for cost per hospitalization was developed to determine the costs of a hospital stay associated with C. difficile and to isolate the financial impacts of both true C. difficile infection and false positives. Relevant predictors of C. difficile positivity used in the model were age, Charlson comorbidity index, white blood cell count, and creatinine. We used CT data to identify and compare 3 inpatient groups: (1) true CDI, (2) C. difficile colonization, and (3) C. difficile negative. Results: A diagnosis of C. difficile adds significantly (>$3,000) to unadjusted hospital cost compared to a negative result. Propensity-adjusted analyses demonstrated that C. difficile colonization was associated with significantly increased (median, $5,000) hospital cost whereas any positive or true diagnoses of C. difficile were not associated with increased cost. Colonized patients also had significantly higher lengths of stay (1 day) and cost per length of stay ($218 per day). Conclusions:This is the first C. difficile cost analysis to utilize PCR CT data to differentiate colonization. Surprisingly, patients with a high CT had disproportionately higher hospital costs compared to matched C. difficile–negative patients, which was not seen among patients with a low CT or with any positive result. We hypothesize that this unexpected finding may be due to misdiagnosis and mistreatment of diarrhea not caused by C. difficile or unadjusted factors associated with high cost and non–C. difficile diarrhea. In addition, the discrepantly high cost attributed to C. difficile diagnosis cited in the literature ($3,000–11,000 per hospitalized case) could be explained by the common use of administrative data to identify C. difficile cases and controls as opposed to our study, which directly linked cost data to C. difficile–positive and –negative test results.

Funding: None

Disclosures: None