Clostridium difficile toxin PCR-8288

Test info

Clostridium difficile toxin PCR
C diff
C. diff

C. difficile positive Toxin PCR will reflex a GDH and Toxin A/B EIA test


Stool, liquid or semi-liquid (the specimen should take the shape of the container)

Screw cap plastic container (non sterile)


Refrigerated (preferred) - 5 days

Ambient - 24 hrs

Frozen (-20°C) - 5 days

  • Formed stools
  • Stool in preservative
  • Rectal swab
  • Endoscopy fluid
  • Other specimen types 
  • More than one stool specimen per day
  • Improper label (unlabeled or mislabeled)
  • Time delay between time of collection and receipt of specimen
  • Improper transport container
  • Improper transport temperature
  • Interfering substances
  • Leaking container


AHL - Microbiology: M
2.5 hours/ same day

Real-Time Polymerase Chain Reaction (RT-PCR)

Clinical and Interpretive info



  • Only test symptomatic patients (diarrhea with 3 or more liquid/loose, unformed stools in 24 hours or less).
    • Testing of asymptomatic patients is not clinically useful.
  • Do not test patients who are having liquid/loose stools for known reasons (i.e. laxatives, bowel prep).
  • Only one specimen is necessary for detection of toxigenic C. difficile.
    • If PCR is negative, repeat testing within 7 days is not recommended.
  • Testing for “test of cure” is not clinically useful and is not recommended.
  • Test information has not been established for patients less than 2 years of age. Up to 50% of infants less than 2 years asymptomatically carry C. difficile and its toxins.
  • Positive C. difficile toxin PCR tests will reflex additional testing, at an additional charge,  to confirm that the patient has existing C. difficile disease as opposed to being colonized or a carrier. 
    • The PCR test detects the gene encoding for C. difficile toxin but does not indicate whether the toxins are actively being produced.  The reflexed EIA (enzyme immunoassay) test will detect GDH antigen, indicating the presence of the organism.  In addition, it will detect the presence of the Toxin A/B. 
    • By using a testing algorithm that utilizes PCR as the first layer of testing the lab is able to screen out most of the negative samples.  If a sample is PCR positive it is reflexed to a less sensitive EIA test to screen out possible carriers, a positive EIA with antigen and toxin detected are considered a true C. difficile infection.
  • Invalid Clostridium difficile Toxin PCR results mean that despite repeat testing, the presence or absence of C. difficile target DNA cannot be determined. This is most likely due to PCR inhibitors in the stool specimen.


87493 - RT-PCR

Additional CPT codes (if indicated)