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HelpTest Code C difficile Toxin C difficile Toxin, PCR
Additional Codes
| Cerner | NextGen |
|---|---|
| C. difficile Toxin | C. difficile Toxin |
| Clostridium difficile Toxin |
Patient Preparation
None required
Collection Instructions
See Microbiology Specimen Collection Manual for Nursing for complete instructions.
Stool for Clostridium Difficile Collection Instructions
General Instructions:
- Do not let urine or toilet bowl water mix with stool during collection. Do not put toilet tissue into collection containers.
- When collecting a stool from a child you may place plastic wrap inside the diaper and then transfer the stool to the appropriate containers provided. Please do not bring a diaper with stool in it to the lab.
- Collect one specimen per day unless otherwise instructed.
Collection:
- Collect the stool specimen in a wide mouthed container, bedpan or clean plastic wrap or plastic bag placed over the toilet seat opening.
- Transfer the entire specimen into the specimen cup provided using the tongue depressor provided or other handy implement such as a plastic spoon.
- Label the stool cup with your full name, date of birth, date and time of collection.
Transport:
- Fresh specimens are the best for testing and the lab should receive specimen as soon as possible after collection (within 2 hours).
- Transport at room temperature.
Specimen Requirements
Unformed samples indicative of CDI
Unpreserved human stool samples.
Transport and store at 2-8 C prior to testing.
Samples should be tested as soon as possible, but may be held up to 24 hours at 20- 30° C or up to 5 days at 2-8 C.
Only liquid or soft stools that take the shape of the container are acceptable. Formed and hard stools will be rejected.
Unformed samples indicative of CDI
Unpreserved human stool samples.
Transport and store at 2-8 C prior to testing.
Samples should be tested as soon as possible, but may be held up to 24 hours at 20- 30° C or up to 5 days at 2-8 C.
Only liquid or soft stools that take the shape of the container are acceptable. Formed and hard stools will be rejected.
Not for children less than 2 years old.
Result Reporting and Reference Values
Results will be reported as C. diff toxin detected/not detected
The normal value is not detected
Reflex Testing
None
Limitations
- This test detects but does not differentiate the NAPI (Ribotype 027) strain from othertoxigenic strains of C. difficile.
- This test targets the tcdB gene for toxin B production. This test will not detect strains of C. difficile that do not contain the tcdB gene.
- Positive results observed with immunocompromised pediatric patients may reflect asymptomatic carriage of C. difficile.
- Detection of C. difficile nucleic acid in stools confirms the presence of these organisms in diarrheal patients but may not indicate that C. difficile are the etiologic agents of the diarrhea.
- Results from the Xpert C. difficile Assay should be interpreted in conjunction with other laboratory and clinical data available to the clinician.
- Erroneous test results might occur from improper specimen collection, failure to follow the recommended sample collection, handling and storage procedures, technical error, sample mix-up, or because the number of organisms in the specimen is too low to be detected by the test. Careful compliance with the instructions in the insert is necessary to avoid erroneous results.
- Because of the dilution factor associated with the retest procedure, it is possible that C. difficile positive specimens, very near or at the limit of detection (LoD) of the Xpert C. difficile Assay, may result in a false negative result upon retest.
- Inhibition of the Gene Xpert C. difficile Assay has been observed in the presence of the following substances: Zinc oxide paste and Vagisil cream.
- False-negative results may occur when the infecting organism has genomic mutations, insertions, deletions, or rearrangements or when performed very early in the course of illness.
- Only patients with 3 or more watery, loose, or unformed stools (stools that take the form of the container) per 24 h qualify for C. diff testing. An important exception is the very rare case where a patient has ileus (obstruction of the intestine due to paralysis of the intestinal muscles) without diarrhea. Any testing of a formed stool specimen should be discussed with the clinician prior to testing to address the issue of ileus.
- Performance characteristics were not established for patients less than 2 years of age.
- Swab specimens are not appropriate samples for C. diff testing.
- The recommended therapy of C. diff includes metronidazole for mild cases and vancomycin or fidaxomicin for moderate to severe cases.
Useful For/ Methodology
The Cepheid Xpert C. difficile Assay, performed on the Cepheid GeneXpert Dx System, is a qualitative in vitro diagnostic test for rapid detection of toxin B gene sequences from unformed (liquid or soft) stool specimens collected from patients suspected of having Clostridioides difficile infection (CDI). The test utilizes automated real-time polymerase chain reaction (PCR) to detect toxin gene sequences associated with toxin producing C. difficile.