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Test Code LAB253 Clostridium Difficile, PCR

Additional Codes

CDT|Clostridium difficile

Test Performed By

Cayuga Medical Center, Main Laboratory

Container Name

Sterile Container (STER CONT)

Day(s) and Time(s) Test Performed

STAT - Monday through Sunday; Continuously

List Price

$239.00

CPT Codes

87493

Temperature

Refrigerated

Specimen Collection Instructions

Formed stools will NOT be accepted for analysis.

 

 A fresh watery, loose or unformed stool sample should be submitted in a clean cup. No preservatives should be used.

 

 Store specimen refrigerated for up to 5 days (preferred) or room temperature for up to 24 hours.

 

Please refer to sidebar Resources for Specimen Collection Instructions.

Specimen Type

Stool

C. difficile Algorithm

The C. difficile PCR test identifies the presence of C difficile DNA (toxin B gene) but does not distinguish between active infection and asymptomatic colonization. The toxin immunoassay identifies toxin production. Using this test protocol to provide both the PCR and toxin results can help clinicians better distinguish between active infection and asymptomatic colonization and may reduce unnecessary treatment of colonized patients. This protocol may also reduce over-reporting of hospital-onset C. difficile cases that represent colonization rather than active infection.

 

A two-step algorithm is used. PCR-negative samples are considered negative. PCR-positive samples are tested for the presence of toxin A/B.

 

PCR-positive, toxin-positive samples collected from a patient with compatible signs and symptoms of CDI indicate that active infection is likely.

 

PCR-positive, toxin-negative samples may represent colonization rather than active infection.

 

Clinical judgement should be used to decide if the patient requires treatment.

Patients that do not exhibit the signs and symptoms associated with CDI or those that have an alternate explanation for the signs and symptoms exhibited are less likely to have an active C. difficile infection. Treatment may not be warranted as the patient is likely colonized.

 

A patient with clear signs and symptoms of CDI that are PCR-positive, toxin-negative may still have active CDI and treatment may be warranted. Clinical judgement must be applied.

 

A negative result obtained using the PCR method is considered a final (negative) result.

 

A positive result obtained using the PCR method reflexes toxin testing.

 

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 indicate C. difficile colonization without active infection. Few patients with CDI may have a negative toxin result. Results should be interpreted in conjunction 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 symptoms suggest active C. difficile infection.

 

PCR-positive, Toxin invalid

Unable to interpret. Suggest repeat collection and testing.

 

Repeat Testing

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 treatment regimen (clinical relapse).

 

Inpatients: Patients found positive should not be retested for 30 days. Patients tested and found negative should not be retested for 7 days. Providers can request testing for urgent exceptions.

Clinical and Interpretive

This assay is useful for the sensitive, specific, and rapid diagnosis of Clostridium difficile-associated diarrhea and pseudomembranous colitis.

 

Clostridium difficile is the cause of Clostridium difficile-associated diarrhea (CDAD), an antibiotic-associated diarrhea, and pseudomembranous colitis (PMC). In these disorders bacterial overgrowth of Clostridium difficile develops in the colon, typically as a consequence of antibiotic usage. Clindamycin and broad-spectrum cephalosporins have been most frequently associated with CDAD and PMC, but almost all antimicrobials may be responsible.

 

Disease is related to production of toxin A and/or 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.

 

This assay also includes testing for the NAP-1 strain, also known as the 027 or BI strain. The NAP-1 strain is a virulent, highly toxigenic strain of Clostridium difficile that is generally resistant to the fluoroquinolones. These strains, which can cause additional infection control concerns because of heavy spore production, may be preferentially treated with oral vancomycin.