Epidemiology and Healthcare Costs of Incident Clostridium difficile Infections Identified in the Outpatient Healthcare Setting

Jennifer L. Kuntz, PhD; Eric S. Johnson, PhD; Marsha A. Raebel, PharmD; Amanda F. Petrik, MS; Xiuhai Yang, MS; Micah L. Thorp, DO, MPH; Steven J. Spindel, MD; Nancy Neil, PhD; David H. Smith, PhD


Infect Control Hosp Epidemiol. 2012;33(10):1031-1038. 

In This Article

Abstract and Introduction


Objective. To describe the epidemiology and healthcare costs of. Clostridium difficile infection (CDI) identified in the outpatient setting.
Design. Population-based, retrospective cohort study.
Patients. Kaiser Permanente Colorado and Kaiser Permanente Northwest members between June 1, 2005, and September 30, 2008.
Methods. We identified persons with incident CDI and classified CDI by whether it was identified in the outpatient or inpatient healthcare setting. We collected information about baseline variables and follow-up healthcare utilization, costs, and outcomes among patients with CDI. We compared characteristics of patients with CDI identified in the outpatient versus inpatient setting.
Results. We identified 3,067 incident CDIs; 56% were identified in the outpatient setting. Few strong, independent predictors of diagnostic setting were identified, although a previous stay in a nonacute healthcare institution (odds ratio [OR], 1.45 [95% confidence interval (CI), 1.13–1.86]) was statistically associated with outpatient-identified CDI, as was age from 50 to 59 years (OR, 1.64 [95% CI, 1.18–2.29]), 60 to 69 years (OR, 1.37 [95% CI, 1.03–1.82]), and 70 to 79 years (OR, 1.36 [95% CI, 1.06–1.74]), when compared with persons aged 80–89 years.
Conclusions. We found that more than one-half of incident CDIs in this population were identified in the outpatient setting. Patients with outpatient-identified CDI were younger with fewer comorbidities, although they frequently had previous exposure to healthcare. These data suggest that practitioners should be aware of CDI and obtain appropriate diagnostic testing on outpatients with CDI symptoms.


Clostridium difficile infection (CDI) is the most common cause of healthcare-associated infectious diarrhea in the United States.[1,2] CDI was once thought to occur almost exclusively among hospitalized patients, an assumption that was partly based on the clustering of the strongest risk factors for CDI (ie, antimicrobial use, advanced age, underlying comorbidity) among hospitalized populations and the surveillance for CDI in the inpatient setting.[2–4] As a result, physicians in ambulatory practice may not consider CDI as a diagnosis among their patients.

Recent research has suggested that CDI is emerging as an important but underdiagnosed infection in the general, nonhospitalized population.[5–11] However, additional evidence is needed to evaluate the potential predictors, outcomes, and healthcare costs associated with CDI identified and managed in the outpatient setting. Furthermore, surveillance for CDI is primarily conducted among inpatients within healthcare facilities and is focused on the setting in which a patient acquired C. difficile.[12] Although these surveillance efforts are effective for the identification of CDIs occurring during hospitalization,[12] they do not account fully for infections that occur or are diagnosed in the outpatient setting. Thus, the prevalence of CDI identified in ambulatory populations is unclear, as are any differences between patients presenting with CDI in the outpatient setting versus the inpatient setting.

To address these knowledge gaps, we conducted a retrospective cohort study to (1) describe the epidemiology of CDI identified in the outpatient setting, (2) estimate healthcare costs among patients with CDI, and (3) provide comparisons in the distribution of potential risk factors among patients with outpatient- versus inpatient-identified CDI.