Clostridioides difficile toxin PCR

Alphabetical Test listing

Clostridioides difficile toxin PCR-8288

Test name:

Test number:

8288

Excellian order number:

LAB8288

Abbreviation:

CDI

Alternate names:

Clostridioides
C diff
C-diff
C. diff

Tests included:

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

Useful for:

Confirmation of active C. difficile infection in symptomatic patients.

Specimen type:

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

Collection container:

Screw cap plastic container (non sterile)

Collection instructions:

Stool specimen collection

Transport container:

Screw cap plastic container (non sterile)

Transport and stability:

Refrigerated (preferred) - 5 days

Ambient - 24 hrs

Reason for rejection:

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

Performing lab:

AHL - Microbiology: M

Days set up:

Daily

TAT:

2.5 hours/ same day

Method:

Real-Time Polymerase Chain Reaction (RT-PCR)

Reference ranges:

Negative

Results that require action (critical):

Positive or invalid (Inpatients only)

Clinical information:

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.
- For invalid specimens, the suggested course of action is to collect a new specimen and order 994/LAB994 Clostridium difficile toxin, molecular detection, PCR, formed stool, performed by Mayo Clinic Laboratories (CDFRP) which uses a different methodology.

CPT codes:

87493 - RT-PCR

Additional CPT codes (if indicated)
87449
87324

Date created:

11/30/2009

Revised date:

12/26/2023

Review date:

12/18/2023