Diagnostic Test Directory

Molecular Genetics Laboratory

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Crohn's Disease (NOD2/Card15: R702W, G908R, 1007fs)

  • Synonyms: Inflammatory bowel disease
  • LIS Mnemonic: MBNOD2

    Collect

    Collect whole blood in a purple top (EDTA) tube.

    Volume Required

    3 mls

    Minimum Required

    1 ml

    Transport

    Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.

    Stability

    Whole blood can be refrigerated until shipment.

    Unacceptable conditions

    Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.

    Specimen Handling

    Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.

Days Performed

Mon - Fri 9:00am to 4:00pm

Reported

2-3 weeks

CPT

81401

Disease Information

Clinical Features:

Crohn’s disease is a chronic inflammatory bowel disease (IBD) due to both genetic and environmental factors. The disease is characterized by chronic relapsing intestinal inflammation, most frequently of the terminal ileum and colon. Bowel inflammation is transmural and discontinuous; it may contain granulomas or be associated with intestinal or perianal fistulas.

Molecular Genetics:

The NOD2/CARD15 gene is located on chromosome 16p12-q21. NOD2/CARD15 encodes a protein involved in bacterial recognition by monocytes. Mutations in NOD2 have been found in patients with Crohn’s disease. Three single nucleotide polymorphisms (SNP’s) in the coding region of NOD2 (R702W, G908R, and 1007fs) were confirmed to be independently associated with susceptibility to CD. Studies have shown that 50% of patients with CD carry at least one SNP, and 17% had two mutations. The patients with two mutations were characterized by a younger age at onset, a more frequent stricturing phenotype, and a less frequent colonic involvement than were seen in those patients who had no mutation. The severity of the disease and extraintestinal manifestations were not different for any of the NOD2 genotypes.

Test Methods:

We offer DNA sequence analysis of the three SNP’s in the coding region of the NOD2/CARD15 gene. PCR amplification and sequencing is performed on three coding exons that contain the SNP’s. The patient’s gene sequence is then compared to a reference sequence. Mutations in other exons, promoters, deep intronic regions and other regulatory regions will not be identified with this assay

Detection Rate:

The analytical sensitivity for sequencing is close to 100%.

Related Tests:

Known mutation analysis of the NOD2 gene is available to family members for point mutations previously identified by sequence analysis.

Results:

Test results with interpretation will be mailed and/or faxed to the referring physician or send out lab following completion of the test. Additional reports will be provided as requested.

Utility:

Variants in the NOD2 gene are neither necessary nor sufficient for the development of Crohn’s disease. The presence of these variants may be helpful for estimating disease severity, but are not useful for the diagnosis or prognosis of disease in the absence of clinical indicators. Since the overall penetrance of these variants in terms of lifetime risk of Crohn’s disease is relatively low, the presence of a NOD2 variant in an unaffected individual is not considered highly predictive of Crohn’s disease even in families with affected relatives. For these reasons, this analysis should not be used as the sole or major determinant of patient care.

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