All strains of C.difficile [C.diff ] produce the common antigen glutamate dehydrogenase (GDH). Some strains also make the toxins TcdA and TcdB, which have been identified as major C.difficile virulence factors and are the primary markers for diagnosis of C.difficile infection (CDI).

Our testing algorithm is as follows.

1) Toxin PCR

  • If negative: no evidence of toxigenic C.diff

  • If positive: Toxin Antigen test for confirmation

2) Toxin Antigen

  • If negative: no evidence of toxigenic C.diff

  • If positive: colonisation with toxigenic C.diff

Sample type

Faeces

Specimen requirements

Non-formed stools from symptomatic patients (three or more episodes of type 5-7 stools within 24 hours, not attributable to any other cause or therapy)

Minimum retesting interval for GDH negative (and GDH positive, Toxin negative) is 7 days

Formed stools, and stools from patients that have tested positive for C.difficile in the previous 28 days (GDH positive and Toxin positive (either Ag or PCR)), will not be tested (definition of formed stool: does not conform to the shape of the sample pot)

Faeces should be sent in a 30ml universal with cap and spoon

Minimum volume

1ml for liquid stools

2-3g for semi formed stools

Frequency of test

Daily

Turnaround time

  • C.diff Toxin PCR - 1 day

  • C.diff Toxin Antigen - 1 day

What to request on EPR

Clostridium difficile screen, faeces