N-CDAD in Canada: Results of the Canadian Nosocomial Infection Surveillance Program 1997 N-CDAD Prevalence Surveillance Project

BACKGROUND:

A 1996 preproject survey among Canadian Hospital Epidemiology Committee (CHEC) sites revealed variations in the prevention, detection, management and surveillance of Clostridium difficile-associated diarrhea (CDAD). Facilities wanted to establish national rates of nosocomially acquired CDAD (N-CDAD) to understand the impact of control or prevention measures, and the burden of N-CDAD on health care resources. The CHEC, in collaboration with the Laboratory Centre for Disease Control (Health Canada) and under the Canadian Nosocomial Infection Surveillance Program, undertook a prevalence surveillance project among selected hospitals throughout Canada.

OBJECTIVE:

To establish national prevalence rates of N-CDAD.

METHODS:

For six weeks in 1997, selected CHEC sites tested all diarrheal stools from inpatients for either C difficile toxin or C difficile bacteria with evidence of toxin production. Questionnaires were completed for patients with positive stool assays who met the case definitions.

RESULTS:

Nineteen health care facilities in eight provinces participated in the project. The overall prevalence of N-CDAD was 13.0% (95% CI 9.5% to 16.5%). The mean number of N-CDAD cases were 66.3 cases/100,000 patient days (95% CI 37.5 to 95.1) and 5.9 cases/1000 patient admissions (95% CI 3.4 to 8.4). N-CDAD was found most frequently in older patients and those who had been hospitalized for longer than two weeks in medical or surgical wards.

CONCLUSIONS:

This national prevalence surveillance project, which established N-CDAD rates, is useful as ''benchmark'' data for Canadian health care facilities, and in understanding the patterns and impact of N-CDAD.Key Words: Canada, CDAD, Clostridium difficile-associated diarrhea, Hospital, Nosocomial diarrhea, PrevalenceNosocomial acquisition and transmission of Clostridium difficile are well known (1-4). Despite efforts to control and prevent infections in health care facilities, nosocomially acquired C difficile-associated diarrhea (N-CDAD) persists; some have reported that the number of N-CDAD infections are increasing (5-10). Although the majority of patients remain asymptomatic following acquisition of C difficile (5), it is still the most commonly identified cause of nosocomial diarrhea (5,11,12). While specific antibiotic therapy for C difficile has reduced morbidity and mortality among people with CDAD (13-15), evidence exists that C difficile infection contributes to patient morbidity (7,10) and significantly impacts hospital costs (15-17).Published literature related to the prevalence of CDAD primarily describes periodic outbreaks or endemic situations in health care facilities (7,10,16-19). Because elderly people and those exposed to large amounts of antibiotics have a higher risk of acquiring CDAD, they are commonly surveyed (15,20,21). Specific wards (eg, medical and surgical) where the rates of CDAD are higher are also more frequently studied (2,6,22,23). Multicentre and national surveillance of CDAD in North America and Europe is rare (24-28). In Canada, individual health centres have data on the prevalence and demographics of CDAD cases (6,9,21); however, no national data exist.Many CDAD surveillance studies include community cases (16,17,24-28); however, it is useful to examine specifically N-CDAD cases, because they represent illness that may be prevented by hospital infection prevention and control practices. The primary reservoirs of C difficile in the hospital are humans and the environment (29). Consequently, the nosocomial acquisition of this organism may represent inadequate infection control practices (30). This underscores the importance of instigating measures to monitor the prevalence of N-CDAD, and implementing and assessing the efficacy of any prevention or control practices.There is no Canadian literature that examines the hospital costs of C difficile infections. Worldwide, there are limited data regarding the hospital costs associated with CDAD (16,17). One British study specifically examined the costs of N-CDAD (15). However, all studies suggest that these costs are substantial, which include the expenses of caring for and treating patients with CDAD, combined with the costs associated with C difficile outbreaks (15-17).An N-CDAD prevalence project was undertaken by the Canadian Nosocomial Infection Surveillance Program (CNISP) through participating Canadian health care facilities. CNISP is a collaborative national surveillance program among the Laboratory Centre for Disease Control, Health Canada and the Canadian Hospital Epidemiology Committee (CHEC), a subcommittee of the Canadian Infectious Disease Society. CHEC members participated voluntarily in the CNISP project. The intent of this project was to establish health care facility N-CDAD prevalence rates that could be used as ''benchmark'' data for other Canadian health care facilities, and to assist with the development and evaluation of guidelines that may decrease the incidence and cost of N-CDAD within Canadian health care facilities. The project used standardized case definitions for CDAD and N-CDAD. Non-nominal data were collected and submitted to the Laboratory Centre for Disease Control for compilation, analysis and interpretation. To estimate the burden of N-CDAD on the Canadian health care system, it was necessary to first determine national N-CDAD prevalence rates through a multicentre, geographically diverse surveillance project.