Clinical Significance

The JAK2 V617F mutation has been identified in up to 97 % of polycythemia vera (PV) and in approximately 50-60% of essential thrombocythemia (ET) and primary myelofibrosis (PMF) cases.  Presence of V617F mutation does not distinguish between these forms of myeloproliferative neoplasm.  Additionally, JAK2 V617F has also been found in approximately 60% of cases of myelodysplastic/myeloproliferative neoplasm (MPN) with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T). A small subset of other myeloid disorders, such as chronic myelomonocytic leukemia, may also harbor JAK2 V617F mutations.

Gene

The V617F mutation in exon 14 of JAK2 (Janus kinase 2 gene) is a high frequency alteration that leads to deregulation of the kinase activity and constitutive tyrosine phosphorylation of the JAK2 protein. In MPN, the V617F mutation is heterozygous in most patients and homozygous only in a minor subset. Mitotic recombination most likely causes both 9p loss of heterozygosity, along with concurrent transition from heterozygosity to homozygosity.

A documented prior authorization will need to be present in Health Link before testing can be performed. 

The ordering source should consult the Genetic Testing at UW Health Clinical Laboratories document on U-Connect prior to ordering testing. Contact UWHC Referral office (608) 262-6388 for questions. 

Do not centrifuge or freeze sample.

Refrigerate specimen. Do not freeze or centrifuge.

Transport specimen to laboratory immediately. Refrigerate specimen if not delivered immediately. Do not freeze sample.

A written interpretive report is provided by the laboratory.

The quantitative range for Jak2 V617F is 5% to 50% mutant. If the Jak2 V617F allele is not detected or the result is below the detection range of 2.5%, a result of "Not detected" will be reported. If the result is greater than 50% allele burden, a result of "Detected, >50%” will be reported. If the result is less than 5% allele burden, a results of “Detected, <5%” will be reported.

 A result of 'Not detected" does not rule out the presence of the Jak2 V617F allele. False negative results may be due to inhibitory substances that may be present in the specimen. Inadequate specimen collection, processing and storage may invalidate test results. This test should not be used as the only criterion to form a clinical conclusion. Instead, results should be correlated with other test results, patient symptoms and clinical presentation.

The performance characteristics of this test were validated by UWHC Clinical Laboratories. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test; however, FDA approval or clearance is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. The UWHC Clinical Laboratories is authorized under Clinical Laboratory Improvement Amendments (CLIA) to perform high-complexity testing.

A professional fee is associated with this test.(CPT Code G0452).