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Recommended protocol for testing for Clostridioides difficile and subsequent culture

Published on 19 October 2016

From: Antimicrobial Resistance and Healthcare Associated Infection Scotland

Describes the methodologies for testing for Clostridioides difficile and subsequent culture.



Although the current gold standard for C. difficile toxin testing is a well-performed cell-culture cytotoxicity assay it:

  • is not available to every laboratory in Scotland
  • is not straightforward to establish or maintain
  • has an in-built delay of up to 3 days before results are available.

Recommendations first published in 2009 led to widespread adoption by Scottish diagnostic laboratories of more rapid toxin immunoassay testing as the basis for diagnosis of C. difficile infection (CDI) as part of a two-step algorithm. Further guidance was issued in 2012 following publication of an evaluation of algorithms for the diagnosis of CDI. Our updated guidance follows the publication in 2016 of new European guidance which summarises the most recent available evidence published since 2009, particularly in light of new diagnostic tests that have become available. This Scottish guidance will be revised on an ongoing basis to take account of further diagnostic developments.

This version of the protocol includes:

  • the new recommendation to test all diarrhoeal stools in patients aged 3 and above, and testing in cases of paralytic ileus
  • the testing protocol, with optional testing for samples with a negative confirmatory test, and use of membrane assays which combine glutamate dehydrogenase (GDH) and Toxin A/B tests
  • the algorithms, with a separate algorithm for membrane assays.

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