Surveillance of Clostridium difficile in Wales

Background: Surveillance of C. difficile in hospital inpatients aged over 65 was made mandatory by the Welsh Assembly Government in January 2005. The Welsh Healthcare Associated Infection Programme (WHAIP), Public Health Wales NHS Trust was charged with developing and facilitating the surveillance programme.

Objective: To describe the epidemiology of C. difficile in hospital inpatients aged over 65 in Wales.

Methods: Records with a C. difficile toxin test result where the patient is over 65 and an inpatient in hospital in Wales are extracted from a data warehouse system called Datastore, used by all the National Health Service hospital microbiology laboratories in Wales. They are loaded into a WHAIP bespoke database for storage and analysis. Locally used codes are mapped to standard codes for patient gender and specialty. Specialty is based on the specialty of the physician requesting the sample. Repeat positives within 28 days are excluded as duplicates. Hospital admissions data specific to the age group is used to calculate rates.

Results:

13164 non-duplicate C. difficile positives were reported between 01/01/2005 and 30/09/2009, giving an overall rate of 15.8/1000 admissions (95% CI: 15.5, 16.1) in inpatients in the over 65 age-group. Rates have increased over almost 4 years of surveillance, although more recent data shows a decreasing trend.  There is a distinct seasonal pattern, with peaks in the winter months. Rates are higher in females than in males (17.4/1000 (95% CI: 17.0, 17.8) vs 13.9/1000 (95% CI: 13.6, 14.3) admissions) and rates increase with increasing age within the over 65 population (66-75 rate: 8.9/1000 (95% CI: 8.6, 9.3); >95 rate: 28.8/1000 (95% CI: 25.7, 32.3)). A specialty was available for 90% (11877/13164) of records. The 5 specialties with the highest numbers of C. difficile reports were general medicine, geriatric medicine, general surgery, trauma and orthopaedics and renal medicine; they accounted for 83% (9867/11877) of all records. Of these specialties, the highest rate was in renal medicine (65.4/1000 admissions).

Conclusions: The surveillance system has allowed the epidemiology of C. difficile in Wales to be described. The increasing trends over time have been fed back to the infection control teams in Wales and potential areas for targeting interventions have been identified.