Effective Monday, September 29, 2014, American Bio-Clinical Laboratory will only perform the molecular DNA Amplification method for Clostridium difficile testing which will replace our current toxin assay. This assay utilizes molecular DNA Amplification to detect toxin gene sequences associated with toxin producing C. difficile. The assay provides a sensitivity of 98.2% and a specificity of 92.8% when compared to the gold standard of toxigenic culture.

This new test methodology provides superior diagnostic accuracy, which eliminates the need for additional or repeat testing of patient samples. This change was made to be in alignment with the latest ASM guidelines for C. difficile testing and to deliver the highest quality patient results.

Please note the following specimen and testing requirements.

  • Limit testing to patients with ≥3 non-formed stool specimens per 24 period.
    Only liquid or soft stools (takes shape of container) are acceptable unless ileus (obstruction) is present.
    Formed stool will be rejected. Patients may be colonized with toxin-producing C. difficile strains that are not causing illness. Therefore, formed stools are not recommended for testing.
  • Rejection of samples for test of cure.
    Repeat testing following a positive test (test of cure) is not recommended since patients may carry toxigenic C. difficile for months after clinical cure. Repeat testing following a positive test is appropriate if the patient improves with therapy and relapses after the completion of a treatment regimen (clinical relapse).
  • Testing will be restricted to 1 specimen per 7 days.
    Molecular tests for C. difficile are highly sensitive and a negative result does not need to be confirmed by a second specimen.

Test ordering information:

Test Name Test Number CPT Sample
CDIFD 653 87493 Liquid or Soft, Unformed Stool


Interpretive Information:
Results will be reported as positive or negative for toxigenic C. difficile.

Positive test:

  • In adults, metronidazole is the treatment of choice except in cases of severe infection or therapeutic failure.

Negative test:

  • C. difficile molecular tests are highly sensitive. Empiric therapy for patients with diarrhea and negative C. difficile test should be avoided.

For additional C. difficile resources, or if you have any additional questions or concerns, please contact the Microbiology lab directly at 323-222-6688.