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Test Code LAB253 Clostridium difficile, DNA with Reflex to Toxin

Important Note

DO NOT SUBMIT FORMED STOOL FOR TESTING.

Performing Lab

Arnot Ogden Medical Center

Ordering Recommendations

Sensitive, specific, and rapid diagnosis of Clostridium difficile-associated diarrhea and pseudomembranous colitis.
Specimens will be tested by PCR method and positive samples will reflex to toxin antigen testing.

Collect

Unformed Stool 
Must conform to the shape of the container
Bristol Stool Chart Type 6 or 7

Collection Device

Sterile Container

Stability (from collection to initiation)

Room Temperature 24 Hours
Refrigerated 5 days

 

 

Storage/Transport Temperature

Room Temperature or Refrigerated

Methodology

Real-Time PCR

Start Date

10/28/2024

Last Review Date

6/24/2025

Performed

Daily

Specimen Handling

Room Temperature or Refrigerated

Reference Interval

Negative
 

Interpretive Data

LIMITATIONS:

  • Non-027/NAP1/BI isolates representing toxinotype XIV will be reported "Toxigenic C. diff POSITIVE; 027 PRESUMPTIVE POSITIVE" using the Xpert C. difficile/Epi Assay.
  • Occasionally, non-027/NAP1/BI isolates representing toxinotypes IV, V and X will be reported "Toxigenic C. diff POSITIVE; 027 PRESUMPTIVE POSITIVE" using the Xpert C. difficile/Epi Assay.
  • The performance of the Xpert C. difficile/Epi Assay was validated using the procedures provided in the package insert only. Modifications to these procedures may alter the performance of the test.
  • Results from the Xpert C. difficile/Epi 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 this 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 C. difficile/Epi Assay, may result in a false negative result upon retest.
  • Inhibition of the Xpert C. difficile/Epi Assay has been observed in the presence of the following substances: Zinc oxide paste and Vagisil® cream.
  • Outbreaks of CDI may be caused by strains other than 027/NAP1/BI.
  • 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.

 

RESULT INTERPRETATION
PCR negative Negative for C. difficile
PCR positive, Toxin negative Possible colonization without infection.
A negative toxin test with a positive C. difficile PCR result may indicated C. difficile colonization without active infection. Few patients with CDI may have a negative toxin result. Results should be interpreted in conjuction with clinical signs and symptoms.
PCR positive, Toxin positive Likely active infection.
A positive toxin test with a positive C. difficile PCR test with compatible signs and symproms suggest active C. difficile infection.
PCR positive, Toxin invalid Unable to interpret. Suggest repeat collection and testing.

Lab Section

Microbiology

Remarks

  • Not intended as test of cure. Specimen must conform to shape of container (loose or runny).
  • Specimens that do not conform to the shape of the container will not be processed.
  • Endoscopic and gastric aspirates are not approved specimen types for the Clostridium difficile PCR test.
  • Submission of more that one specimen in 7 days is not recommended. It is not necessary to confirm negative results due to high sensitivity of this method. 
  • If testing has been performed in the preceding 7 days and results were negative, the specimen will be rejected as a duplicate.
  • If testing has been performed in the preceding 30 days and results were positive, the specimen will be rejected as a duplicate.
  • Positive tests will reflex to Toxin A/B EIA testing.

Reported

Same shift

Specimen Preparation

Collect unformed stool sample in a clean dry container without preservative.

Pediatric Collection

This testing is not recommended for patients under the age of two.