Clostridium difficile (C.diff)
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) GDH Antigen
- If negative » no evidence of CDI, no further testing required
- If positive » Toxin Antigen test
2) Toxin Antigen
- If positive » consistent with CDI, no further testing required
- If negative » Toxin PCR
3) Toxin PCR
- 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 GDH - 1 day
C.diff Toxin Antigen - 1 day
C.diff Toxin PCR - 1 day
What to request on EPR
Clostridium difficile screen, faeces
Last reviewed:24 September 2024