Special Precautions/Comments:

N.B. This test may be added to samples requesting routine enteric PCR, this will done by the BMS laboratory staff.

Samples will NOT be processed if:

• Patients have had a negative GDH result in the preceding 24 hours.
• Patients have had a positive result within the previous 10 days (unless requested by a medical microbiologist).
• Sample are formed/solid (BSC 1-4).
• Sample is from a child under 2 years of age.

Interferences:  Interference may be encountered with certain samples containing antibodies directed against reagent components. For this reason, assay results should be interpreted taking into consideration the patient’s history and the results of any other tests performed.

Method:  Enzyme immunoassay (EIA) screening test for the detection of GDH. Samples positive for GDH will be tested for Toxin A+B. Toxin A+B is initially tested by EIA; further testing will be completed by automated real-time polymerase chain reaction (PCR). C. difficile ribotyping must be requested by a Consultant Microbiologist.   Calibration: N/A (EIA). Cepheid (PCR).  EQA scheme: NEQAS EQA scheme. IQC: Assay kit controls (Launch Diagnostics).

Interpretation:  GDH results will be reported as Positive or Negative. Toxin results will follow all positive GDH results, these will be be reported as Positive, Equivocal or Negative. Clinical comments will be provided by a Consultant Microbiologist as appropriate.

Additional Information:

Background:  The purpose of the examination is to detect the presence of Clostridioides difficile antigen, glutamate dehydrogenase (GDH) in faecal specimens and the subsequent detection of C. difficile toxins A and/or B in GDH positive samples. GDH is produced by all strains of C. difficile in high quantities.

C. difficile has been found to be the major etiologic agent of antibiotic-associated pseudomembranous colitis (PMC). PMC is a clinically defined syndrome, associated with a recent history of antibiotic use. If unrecognized or untreated, the disease can be fatal. C. difficile has also been implicated in antibiotic-associated colitis and antibiotic-associated diarrhoea.

Nosocomial acquisition of C. difficile infection (CDI) is a serious consideration for some institutions, particularly those with high inpatient populations, chemotherapy wards, or long term patient care.

C.difficile isolates vary in their ability to produce toxins: some do not produce either toxin B or toxin A (non-toxigenic strains). Only toxigenic strains can cause diarrhoea and they always produce toxin B, often in combination with toxin A.

Keywords: C.diff, faeces, stool, CDI, diarrhoea, GDH