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HelpTest Code CDPCR Clostridioides difficile Toxin, PCR, Feces
Ordering Guidance
This test is validated for unformed (liquid or soft) fecal specimens collected from patients suspected of having Clostridioides difficile infection.
Specimen Required
The high sensitivity of amplification by polymerase chain reaction requires the specimen to be processed in an environment in which contamination of the specimen by Clostridioides difficile toxin DNA is unlikely.
Submit only 1 of the following specimens:
Preferred:
Specimen Type: Preserved feces
Supplies: Culture and Sensitivity Stool Transport Vial (T058)
Container/Tube: Commercially available transport system specific for recovery of enteric pathogens from fecal specimens (15 mL of nonnutritive transport medium containing phenol red as a pH indicator, either Cary-Blair or Para-Pak C and S)
Specimen Volume: Representative portion of feces; 5 mL
Collection Instructions:
1. Collect fresh fecal specimen and submit in container with transport medium.
2. Place feces in preservative within 2 hours of collection.
Specimen Stability Information: Ambient (preferred) <5 days/Refrigerated <5 days
Acceptable:
Specimen Type: Unpreserved feces
Supplies:
-Stool container, Small (Random), 4 oz Random (T288)
-Stool Collection Kit, Random (T635)
Container/Tube: Fecal container
Specimen Volume: Representative portion of feces
Collection Instructions: Collect fresh fecal specimen and submit representative sample in fecal container.
Specimen Stability Information: Refrigerated (preferred) <5 days/Frozen <5 days
Useful For
Sensitive, specific, and rapid diagnosis of Clostridioides (Clostridium) difficile-associated diarrhea and pseudomembranous colitis
The test is not recommended as a test of cure.
Testing Algorithm
For more information see Laboratory Testing for Infectious Causes of Diarrhea.
Special Instructions
Method Name
Real-Time Polymerase Chain Reaction (PCR)/Reverse Transcription-(RT) PCR
Reporting Name
C. difficile Toxin, PCR, FSpecimen Type
FecalSpecimen Minimum Volume
See Specimen Required
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Fecal | Varies | 5 days |
Reject Due To
| Feces in gel transport medium ECOFIX preservative Formalin or polyvinyl acetate (PVA) fixative Preserved feces received frozen |
Reject |
Clinical Information
Clostridioides difficile (formerly Clostridium difficile) is the cause of C difficile-associated diarrhea (CDAD), an antibiotic-associated diarrhea, and pseudomembranous colitis (PMC). In these disorders bacterial overgrowth of C difficile develops in the colon, typically as a consequence of antibiotic usage. Clindamycin and broad-spectrum cephalosporins have most frequently been associated with CDAD and PMC, but almost all antimicrobials may be responsible. Disease is related to production of toxin A and B.
Treatment typically involves withdrawal of the associated antimicrobials and, if symptoms persist, orally administered and intraluminally active metronidazole, vancomycin, or fidaxomicin. Intravenous metronidazole may be used if an oral agent cannot be administered. In recent years, a more severe form of CDAD with increased morbidity and mortality has been recognized as being caused by an epidemic toxin-hyperproducing strain of C difficile (NAP1 strain). Many toxin-hyperproducing isolates also contain the binary toxin gene and are resistant to quinolones. This test does not differentiate between toxin-hyperproducing and non-toxin-hyperproducing strains.
Traditionally, diagnosis relied upon:
1. Clinical and epidemiologic features
2. Culture, which is labor intensive and time consuming
3. Cytotoxicity assays, which are labor intensive and time consuming
4. Toxin detection immunoassays, which are insensitive
This test uses a polymerase chain reaction assay that detects the regulatory gene (tcdC) responsible for production of toxins A and B. This test is used for rapid diagnosis of CDAD and PMC, enabling prompt treatment that may reduce hospital stays for inpatients with CDAD.
Reference Values
Negative
Interpretation
Positive: Toxin producing Clostridioides (Clostridium) difficile target nucleic acid is detected.
Negative: C difficile target nucleic acid is not detected.
Cautions
The assay must be performed on fresh feces, fresh-frozen feces, or feces in transport medium.
The assay has not been validated as a test of cure. Since nucleic acid may persist after effective treatment, follow-up testing of a positive result is not recommended.
Interfering substances in the feces may affect the accuracy of the assay; results should always be interpreted in conjunction with clinical and epidemiologic findings.
Submission of more than one specimen for testing is not recommended.
Testing has not been validated for colostomy-, ileostomy-, or colonoscopically-collected specimens.
Patients may asymptomatically carry Clostridioides difficile; clinical correlation is needed when deciding how to manage patients with a positive test result.
Method Description
Test is performed on the Cepheid GeneXpert Dx System, which automates and integrates sample purification, nucleic acid amplification, and detection of the target sequence in simple or complex samples using real-time polymerase chain reaction (PCR) and reverse transcription PCR assays. The system requires the use of single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, cross-contamination between samples is eliminated.
The Cepheid Xpert C difficile/Epi Assay is a qualitative in vitro diagnostic test for rapid detection of toxin B gene sequences and for presumptive identification of 027/NAP1/BI strains of toxigenic Clostridioides (Clostridium) difficile from patients suspected of having C difficile infection (CDI). Presumptive identification of 027/NAP1/BI strains of C difficile is by detection of binary toxin gene sequences and the single base pair deletion at nucleotide 117 in the tcdC gene. The tcdC gene encodes for a negative regulator in C difficile toxin production.
The Xpert C difficile/Epi Assay is intended as an aid in the diagnosis of CDI. Detection of 027/NAP1/BI strains of C difficile by the Xpert C difficile/Epi Assay is presumptive and is solely for epidemiological purposes and is not intended to guide or monitor treatment for C difficile infections. Concomitant culture is necessary only if further typing or organism recovery is required.(Package insert: Xpert C difficile /Epi. Cepheid; Rev. J, 04/2020)
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 dayPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
87493
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CDPCR | C. difficile Toxin, PCR, F | 54067-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| TCDRR | C. difficile Toxin, PCR | 54067-4 |