Diagnostic testing for Clostridium difficile: a comprehensive survey of laboratories in England.

Recent studies have shown poor performance of commonly used toxin enzyme immunoassays (EIAs) for laboratory testing for Clostridium difficile infection (CDI). In 2009-2010, the UK Health Protection Agency and the European Society of Clinical Microbiology and Infectious Diseases stated that toxin EIA testing alone is suboptimal, and recommended a two-step testing protocol (i.e. screening with one method and confirming the results with another method). All acute English National Health Service trusts were surveyed to determine their testing methods and positivity rates using freedom of information requests. Replies were received from 168 of 170 trusts (99% response rate). Seventy percent of trusts were using a toxin EIA as a standalone testing method, with positive predictive values (PPVs) as low as 20% in some cases. The mean positivity rate decreased from 6.45% in 2008 to 4.47% in 2009, which will have a negative effect on the PPVs of these tests. The UK Department of Health publishes CDI rates as a measure of quality of care and good infection control practice. However, this may not provide valid comparisons because of the wide disparity between testing methods. The present study demonstrates wide variation in testing practices for CDI in England, and laboratories should reconsider their current testing strategies.