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Surveillance of Clostridium difficile associated disease (CDAD)

  • Document type:
    Publication
  • Author:
    Department of Health
  • Published date:
    26 August 2005
  • Primary audience:
    Professionals
  • Publication format:
    Electronic only
  • Gateway reference:
    2005
  • Copyright holder:
    Crown

Surveillance of Clostridium difficile associated disease (CDAD) has been included in the mandatory healthcare associated infection surveillance system for acute Trusts in England since January 2004. This scheme is co-ordinated by the Health Protection Agency (HPA) on behalf of the Department of Health. Data are collected quarterly from each of the 169 acute NHS Trusts in England that treat patients aged 65 years and over (children's Trusts are excluded) by Health Protection Agency (HPA) Local and Regional Services Division (LARS) and sent to the Centre for Infections (CfI, HPA) for collation and analysis.

Mandatory Reporting of Cases

Acute NHS Trusts in England are required to report all cases of CDAD in patients aged 65 years and over.  This applies whether the C. difficile is considered to have been acquired in that Trust, in another hospital, or in the community (e.g. in healthcare facilities, a nursing home, residential care facilities or from patients at home).  Cases are defined as all diarrhoeal specimens that test positive for C. difficile toxin (where the patient has not been diagnosed with CDAD in the preceding four weeks).  All data are provisional.

Mandatory Sampling and Strain Characterisation

Testing for the presence of C. difficile relies on detection of C. difficile toxins A and B.  It is not necessary for the bacteria to be cultured; hence samples are not always routinely available for strain characterisation and investigation of outbreaks.  Recently, increasing numbers of hyper-toxin producing strains identified as 027 have been reported in England, several in relation to local outbreaks.  This strain had been reported previously in North America.

C. difficile strain characterisation is being investigated further by random sampling of Trusts across regions in England, through the mandatory C. difficile sampling scheme which began in January 2005.  The results of these investigations will be published when the first year of sampling is complete.  There was no systematic examination of strains from outbreaks or Trusts with high endemicity during the first year of mandatory CDAD surveillance.

This report describes the data collected during the first year of the mandatory surveillance scheme (January - December 2004).

The tables give data on numbers and rates of C. difficile associated disease (CDAD) reported by NHS acute Trusts: Mandatory surveillance, January - December 2004.

Source of bed-days denominator data: Hospital Episode Statistics (HES), Information Centre for health and social care.

National data

  • The total number of reports of CDAD in England between January and December 2004 was 44,488 for 166 Trusts (including four Trusts who had no cases to report).
  • Two Trusts did not submit any data, and one Trust did not submit data for three quarters. This was primarily due to IT problems.
Interpretation of the data

The data are complex and consequently need to be interpreted with care, taking the following into account:

  • This is the first year of the surveillance scheme and the recommendations from the National Clostridium difficile Standards Group may not have been followed consistently.  The HPA is working closely with Trusts to improve both compliance with the reporting guidelines and ascertainment, where reports are incomplete or not returned.
  • The CDAD cases reported by an acute Trust were not necessarily acquired in that Trust.  The Standards Group recommended that C. difficile data should include source information for the specimen (e.g. hospital, community), providing a means of distinguishing hospital from community-acquired cases.  It is apparent that Trusts may not be able to make this distinction.  In the past it was considered that C. difficile acquired in the community was an unusual event.  Anecdotally six Trusts have reported that 18-30% of their Trust's reports were not from patients in the acute Trust.  This finding requires further investigation.  The distinction between hospital and community acquired cases is difficult not least because many patients with CDAD will have had recent hospital treatment. 
  • The number of CDAD reports for an acute Trust will include reports of samples sent to that acute Trust's laboratories from NHS healthcare facilities not run by an acute Trust (e.g. from PCT-run community hospitals, or General Practitioners).  The use of HES data is the first step in identifying an appropriate denominator for the surveillance of healthcare-associated infections in patients aged 65 years and over.  However, the HES denominator data for each acute Trusts presented here includes only the bed-days for hospitals run by that acute Trust.  The bed-days listed for each acute Trust therefore frequently do not adequately represent the volume of patients served by an acute Trust's laboratories.  The result is that some Trusts, in particular those that receive a large proportion of their samples from outside of their Trust, have higher rates of CDAD calculated than relates to the hospital inpatients.  
  • The bed occupancy figures used to derive the CDAD rates for 2004 are for patients aged 65 years and over from a period before the CDAD data (April 2003 to March 2004).  This is the most recent denominator data available. A Trust's rate may be affected if there has been a significant change in activity that is not yet reflected in the bed occupancy figure for 2003-4. The rates published here are provisional and will be updated when the bed occupancy figures for the appropriate period are available.
  • All the bed occupancy figures used to calculate the rates apply only to overnight admissions. Consequently CDAD in patients who are not admitted overnight, may make a Trust's rate look falsely high, as these patients will feature in the numerator but not in the denominator. 
  • Specimens should be tested using toxin tests that detect C. difficile toxins A and B.  Some Trusts, due to contracts with suppliers of test-equipment may be continuing to only test for toxin A.  This may have resulted in a small number of CDAD cases not being recognised.
  • Report of C.difficile in patients receiving independent healthcare may be included in the C. difficile reports from some Trusts. This has been indicated where known.  Further work is in progress to clarify this area of ascertainment and the extent to which these patients may have acquired their infection whilst in the community.

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