JAK2 V617F Mutation Detection, Blood (JAK2B)

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Marshfield Clinic Public WebSite

Test Code: JAK2SO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Janus kinase 2 gene, 83872-JAK2B, Tyrosine Kinase Mutation

Useful For

Aiding in the distinction between a reactive blood cytosis and a chronic myeloproliferative disorder in peripheral blood specimens

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Whole blood EDTA	EDTA Lavender Top Tube (LTT)	Yellow ACD	4 mL	1 mL

Collection Processing Instructions

Specimen must arrive at Mayo within 168 hours (7 days) of draw.

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information

Specimen Type	Temperature	Time
Whole blood EDTA	Ambient (preferred)	7 days
Whole blood EDTA	Refrigerated	7 days

Rejection Criteria

Hemolysis
Moderately to severely clotted

Interference

A positive result is not specific for a particular subtype of myeloproliferative neoplasm and clinicopathologic correlation is necessary in all cases. If this test is ordered in the setting of erythrocytosis and suspicion of polycythemia vera, interpretation requires correlation with a concurrent or recent prior bone marrow evaluation.

A negative result does not exclude the presence of a myeloproliferative neoplasm or other neoplastic process.

In rare cases, a variant other than the V617F may be present in an area that interferes with primer or probe binding and cause a false-negative result.

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Analytical Time	Methodology/Instrumentation
Mayo Clinic Laboratories	Monday through Friday	2-5 days	Point Mutation Detection in DNA Using Quantitative Polymerase Chain Reaction (PCR)

Reference Lab

Mayo Clinic Laboratories

Test Information

The Janus kinase 2 gene (JAK2) codes for a tyrosine kinase (JAK2) that is associated with the cytoplasmic portion of a variety of transmembrane cytokine and growth factor receptors important for signal transduction in hematopoietic cells. Signaling via JAK2 activation causes phosphorylation of downstream signal transducers and activators of transcription (STAT) proteins (eg, STAT5) ultimately leading to cell growth and differentiation. BCR-ABL1-negative myeloproliferative neoplasms (MPN) frequently harbor an acquired single nucleotide variant in JAK2 characterized as c.G1849T; p. Val617Phe (V617F). This variant is identified overall in approximately two-thirds of all MPN,(1-3) but the prevalence varies by MPN subtype. The JAK2 V617F variant is present in 95% to 98% of polycythemia vera patients, 50% to 60% of primary myelofibrosis patients, and 50% to 60% of essential thrombocythemia patients. It has also been described infrequently in other myeloid neoplasms, including chronic myelomonocytic leukemia and myelodysplastic syndrome.(4) This variant is not seen in chronic myelogenous leukemia (CML) or in reactive conditions with elevated blood counts. Detection of the JAK2 V617F variant is useful to help establish the diagnosis of MPN. However, a negative JAK2 V617F result does not indicate absence of a MPN. Other important molecular markers in BCR-ABL1-negative MPN include CALR exon 9 variant (20%-30% of PMF and ET) and MPL exon 10 variant (5%-10% of PMF and 3%-5% of ET).(5-9) Variants in JAK2, CALR, and MPL are essentially mutually exclusive.

Reference Range Information

Interpretive report

Interpretation

The results will be reported as 1 of the 2 states:

-Negative for JAK2 V617F mutation

-Positive for JAK2 V617F mutation

Positive variant status is highly suggestive of a myeloid neoplasm, but must be correlated with clinical and other laboratory features for definitive diagnosis.

Negative variant status does not exclude the presence of a myeloproliferative neoplasm or other neoplasm.

Results below the laboratory cutoff for positivity are of unclear clinical significance at this time.

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
81270