Decision models to improve healthcare-associated C. difficile PCR test use in patients with community-acquired pneumonia

Adults hospitalized with community-acquired pneumonia (CAP) typically receive antibiotics and thus are at increased risk of developing Clostridioides difficile infection (CDI), a disease of significant morbidity. We developed and validated a CAP-specific clinical decision algorithm to facilitate optimal diagnostic stewardship of C. difficile polymerase chain reaction (PCR) testing. The study was a single-center retrospective, case-control analysis of hospitalized adult patients empirically treated for CAP between January 1, 2014 and May 29, 2018. A series of predictive models and validity assessments were used to evaluate demographic and post-admission patient-specific risk factors as predictors of CDI case status among patients with CAP. Thirty-two PCR confirmed CDI cases were identified and 232 randomly selected controls were drawn from the total CAP population. After propensity score weighting, hospital-onset (HO) CDI was significantly associated with broad-spectrum Gram-negative antibiotic use (P=0.002) as was subsequent community-onset (CO) CDI (P=0.005). Modified-APACHE II > 8.5 (P=0.003) and broad-spectrum Gram-negative antibiotic use (P=0.002) were associated with healthcare-associated CDI and were robust in multiple validity analyses. Patients with m-APACHE II [≤] 8.5 who received broad-spectrum Gram-negative antibiotics were more likely (odds=1:2) to experience healthcare-associated CDI compared to those who did not receive these broad-spectrum agents (odds=1:125) and compared to those with m-APACHE II > 8.5 irrespective of treatment (odds=5:27). We conclude that broad-spectrum Gram-negative antibiotic use was the common factor in development of CDI in patients with CAP in all settings. Prospective studies are needed to confirm the reproducibility and clinical utility of our model when used for diagnostic test stewardship.