26348 Polycythemia Vera, JAK2 V617F with Reflex to JAK2 Exon 12-15, Sequencing for Erythrocytosis, Varies (PVJAK)

JAK2 V617F

JAK2 exon 12

Polycythemia Vera

Myeloproliferative Neoplasm (MPN)

The algorithm starts with a highly sensitive DNA-based JAK2 V617F test by allele specific polymerase chain reaction. If the JAK2 V617F result is negative or very low positive (0.06% - 2%), JAK2 exon 12-15 Sanger sequencing test will be performed on the stored RNA sample. If a JAK2 V617F mutation (>2%) is detected, the algorithm stops and no further testing will be performed.

The Sanger sequencing covers JAK2 exons 12 through the first 90% of exon 15, which spans the region containing essentially all mutations reported in myeloproliferative neoplasms. 

​Aiding in the distinction between the myeloproliferative neoplasm polycythemia vera (PV) and other secondary erythrocytosis

Blood:

1. Invert several times to mix blood.

2. Send whole blood specimen in original tube. Do not aliquot.

3. Label specimen as blood.

Bone Marrow:

1. Invert several times to mix blood.

2. Send bone marrow specimen in original tube. Do not aliquot.

3. Label specimen as bone marrow. 

Specimen must arrive within 5 days (120 hours) of collection.

The following information is required:

1. Pertinent clinical history

2. Clinical or morphologic suspicion

3. Date of collection

4. Specimen source

​A positive result is not specific for a particular diagnosis. Correlation with clinicopathologic findings and other laboratory results 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.

​The Janus kinase 2 (JAK2) gene 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. The JAK2 V617F mutation is located in exon 14 and present in 50% to 60% of primary myelofibrosis and essential thrombocythemia and in 95% to 98% of polycythemia vera (PV). In the rest of the PV cases, over 50 different mutations have been reported within exons 12 through 15 of JAK2, and essentially all non-V617F JAK2 mutations have been identified in PV. These mutations include point alterations and small insertions or deletions. Several of the exon 12 mutations have been shown to have biologic effects similar to those caused by the V617F mutation such that it is currently assumed other nonpolymorphic mutations have similar clinical effects. However, some mutations may not be well characterized and require further clinical and research evaluation. 

The results will be reported as 1 of the 3 following states:

-Positive for JAK2 V617F mutation

-Positive for JAK2 mutation (other than V617F)

-Negative for JAK2 mutations

If the result is positive, a description of the mutation at the nucleotide level and the altered protein sequence are reported.

A positive mutation status is highly suggestive of a myeloid neoplasm and may support a diagnosis of polycythemia vera in the appropriate clinical setting. Correlation with clinicopathologic findings and other laboratory results is necessary in all cases.

A negative mutation status makes a diagnosis of polycythemia vera highly unlikely, although it does not completely exclude this possibility, other myeloproliferative neoplasms or other neoplasms.​