Clostridium difficile Toxin Gene, NAA

CPT: 87493
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Test Details

Use

Aid in the diagnosis of antibiotic-associated diarrheal disease and pseudomembranous colitis. Toxigenic C difficile is a major cause of antibiotic-associated diarrhea and colitis and is the causative agent for virtually all cases of pseudomembranous colitis. Although about 2% of normal healthy adults are colonized with C difficile, many patients acquire this organism through nosocomial infection. Exposure to most antibiotics is thought to allow proliferation of toxigenic C difficile by disrupting the normal intestinal flora. Two large toxin proteins, toxin A and toxin B, encoded by two separate genes, named tcdA and tcdB, are believed to be the primary virulence factors of C difficile. Together, with three additional genes, they form a 19.6-kb pathogenicity locus called PaLoc, which is found in all known toxigenic strains of C difficile.

Limitations

• This test does not distinguish between viable and nonviable organisms.

• Test results are to be used in conjunction with information available from the patient's clinical evaluation and other diagnostic procedures.

• This test is for use with unformed (ie, soft, loose) stool samples only.

• This test detects/presumptively differentiates the BI/NAP1/027 strain from other toxigenic strains of C difficile. Detection of BI/NAP1/027 strains of C difficile is presumptive and is solely for epidemiological purposes and is not intended to guide or monitor treatment for C difficile infections.

• The detection of bacterial nucleic acid is dependent on proper specimen collection and handling (including transportation and storage).

• Performance characteristics have not been established for patients less than two years of age.

Methodology

Real-time polymerase chain reaction (PCR)

Reference Interval

Negative

Additional Information

During the last several years, increased rates of C difficile infection have been reported, noting more severe disease and an associated increase in mortality. C difficile infection remains a disease mostly associated with health care (at least 80%), with the elderly remaining at greatest risk. More disease has been reported in traditionally "low-risk" individuals, such as healthy persons in the community and peripartum women. Severe disease outbreaks of C difficile infection in health care facilities have been attributed to the emergence of a hypervirulent epidemic strain, known by its names—assigned by various typing schemes—as restriction enzyme analysis type BI, North American Pulsed Field type 1 (NAP1), or PCR ribotype 027. BI/NAP1/027 has spread widely, and it appears more virulent due to its increased production of toxins A and B and its production of an additional toxin known as binary toxin. This strain is also believed to produce more spores, leading to enhanced persistence in the environment.

Specimen Requirements

Specimen

Stool (unformed)

Volume

5 g

Minimum Volume

0.5 g or 0.5 mL liquid stool

Container

Sterile screw-cap container or stool transport without preservatives (Para-Pak® white clean vial). "Cool Whip" containers, denture cups, or other similar containers often leak or even explode during transport and may be rejected by the laboratory.

Storage Instructions

Specimen should be kept at 2°C to 8°C and transported to the laboratory within 24 hours of collection. Do not freeze.

Causes for Rejection

Unlabeled specimen or name discrepancy between specimen and test request label; quantity insufficient; formed stools; frozen stool; stool in preservative; specimens other than stool; improper storage or transport device; grossly leaking specimens; specimen older than 24 hours that is stored at room temperature, or specimen older than five days stored at 2°C to 8°C

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
183988 C difficile Toxin Gene NAA 54067-4 183989 C difficile Toxin Gene NAA 54067-4

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CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2017, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf