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


Between June 1, 2005, and September 30, 2008, we identified 3,067 CDIs. Of these, 1,712 (56%) were identified in the outpatient setting. Among CDI cases in the outpatient setting, 62% were identified through a positive toxin test, with the remaining 38% being identified through an ICD-9 code alone. All of the CDIs identified in the outpatient setting through a positive toxin test also received treatment for CDI.

The majority of CDIs occurred among persons 65 years and older, although individuals with outpatient-identified CDI were, on average, nearly 7 years younger than those with inpatient-identified CDI (Table 1). Persons with outpatient-identified CDI were less likely to have a history of hospitalization or a stay in a nonacute healthcare institution than those with inpatient-identified CDI (Table 1). Furthermore, the majority of comorbid conditions was less prevalent among patients with outpatient-identified CDI in the 1 year before infection (Table 2).

Antimicrobials were dispensed from an outpatient pharmacy to 78% of persons with outpatient-identified CDI in the previous 60 days (Table 3). The percentage of patients with outpatient-identified CDI who received an outpatient antimicrobial dispensing increased to 86% when the exposure time window was increased to 180 days. Patients with CDI had commonly received fluoroquinolones (outpatient-identified CDI, 30%; inpatient-identified CDI, 33.6%) or cephalosporins (outpatient-identified CDI, 20.6%; inpatient-identified CDI, 20.3%; Table 3). Furthermore, persons with outpatient-identified CDI received gastric acid suppression, statins, and chronic oral corticosteroids from an outpatient pharmacy less frequently than persons with inpatient-identified CDI, although these medications were received by a minority of patients (Table 3).

Nearly half (45%) of outpatient-identified CDI cases and about one-fourth (26.9%) of inpatient-identified CDI cases were associated with an additional CDI-related outpatient visit in the 180 days following infection (Table 4). Emergency department visits were far less common, at 5.7% and 2.7% for outpatient-identified and inpatient-identified CDI, respectively. The majority of patients with outpatient-identified CDI received at least 1 and, on average, 3.7 dispensings of CDI-related medication on or following their date of infection (Table 4). Further, of patients with outpatient-identified CDI, 10.5% were hospitalized with a CDI-related diagnosis code during the follow-up period. These hospitalizations occurred, on average, 27 days following outpatient identification of CDI and lasted an average of 10 days (Table 4). Additionally, 9.8% of persons with outpatient-identified CDI and 32.5% of persons with inpatient-identified CDI died from any cause in the 180 days following infection.

Outpatient care costs were higher among persons with CDI identified in the outpatient setting, with pharmacy representing the greatest percentage of these costs in either group. Similarly, patients with inpatient-identified CDI had higher inpatient costs than patients with outpatient-identified CDI ($10,708.40 vs $837.40; Table 5).

The logistic regression model utilized 1,279 outpatient-identified CDIs and 1,131 inpatient-identified CDIs (21% were removed because of missing values). Few individual patient characteristics were significantly associated with identification of CDI in the outpatient setting (Table 6). However, collectively, the 21 characteristics in the model discriminate CDIs identified in the outpatient setting from inpatient-identified CDIs with moderate effectiveness (c-statistic, 0.76). After controlling for all other covariates, a previous stay in a nonacute healthcare institution (OR, 1.45 [95% confidence interval (CI), 1.13–1.86]) was statistically associated with outpatient-identified CDI (Table 6). 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 age from 80 to 89 years, was also associated with outpatient-identified CDI.