Date of Degree

2010

Document Type

PhD diss.

Degree Name

PhD (Doctor of Philosophy)

Department

Epidemiology

First Advisor

Elizabeth Chrischilles

Abstract

Clostridium difficile infection (CDI) is the most common cause of hospital-acquired infectious diarrhea in the United States. Although C. difficile is widely-recognized as a pathogen among hospitalized populations, CDI has emerged in the community setting but is under-diagnosed. This study sought to increase knowledge about the incidence of, risk factors for, and outcomes associated with community-associated CDI (CA-CDI).

A retrospective nested case-control study was conducted using insurance claims data from the Wellmark Data Repository for the time period between January 1, 2003 and December 31, 2007. Persons with CDI were identified and were classified as community-associated CDI and hospital-acquired CDI. During this time, 304 cases of CA-CDI and 338 cases of HA-CDI were identified. Within this population, the incidence rate for CA-CDI was 11.16 cases per 100,000 person-years, whereas the incidence rate for HA-CDI was 12.41 cases per 100,000 person-years.

Conditional logistic regression was utilized to determine the risk for CA-CDI related to pharmacologic exposures, comorbidity, demographic characteristics, and healthcare utilization. Prior to controlling for other risk factors and covariates; being over the age of 50 years, gender, history of hospitalization, number of outpatient physician visits, antimicrobial use, gastric acid suppressant use, underlying comorbidity, and diagnosis of gastrointestinal disease (including IBD, diverticular disease, GERD) were associated with the development of CA-CDI. However, after adjustment for all covariates, increased risk for CA-CDI within this population was consistently associated with antimicrobial use, being between the age of 19 and 74 years, and diagnosis of inflammatory bowel disease. Gastric acid suppressant use was a risk factor in a number of models, although this association was not consistent. Furthermore, persons who last received antimicrobials in the previous 150 days and persons who received a greater number of different antimicrobial agents were at increased risk for CA-CDI.

Antimicrobial use was the primary risk factor for CA-CDI, although 27% of cases did not have prior exposure to antimicrobials. In fact, 17% of CA-CDI cases did not have any of the traditional risk factors for CDI (i.e., no antimicrobial or gastric acid suppressant exposure, no underlying illness, and no history of hospitalization). Furthermore, none of the CA-CDI cases underwent surgical procedures attributable to CA-CDI, although approximately 25% of CA-CDI cases were hospitalized with a diagnosis of CDI.

This research demonstrates that CDI is occurring in the community setting and in populations that were previously not considered to be at risk. In this study, the risk factors for CA-CDI were similar to those identified in hospitalized populations, although it was not uncommon for persons to develop CA-CDI without any of these risk factors. Furthermore, the characteristics of persons with CA-CDI and the outcomes in this group were different than those previously reported among hospital-acquired CDI cases. Collectively, this study provides valuable knowledge about the epidemiology of CA-CDI and serves as a foundation for future research.

Pages

xiii, 224

Bibliography

207-224

Copyright

Copyright 2010 Jennifer Lee Kuntz