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Test Code JAKXR JAK2 Exon 12-15 Sequencing, Polycythemia Vera Reflex


Specimen Required


Only orderable as a reflex. For more information, see PVJAK / Polycythemia Vera, JAK2 V617F with Reflex to JAK2 Exon 12-15, Sequencing for Erythrocytosis.


Useful For

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

 

Evaluating for mutations within exons 12 to 15 of JAK2 in an algorithmic process as part of PVJAK / Polycythemia Vera, JAK2 V617F with Reflex to JAK2 Exon 12-15, Sequencing for Erythrocytosis

Method Name

Only orderable as a reflex. For more information, see PVJAK / Polycythemia Vera, JAK2 V617F with Reflex to JAK2 Exon 12-15, Sequencing for Erythrocytosis.

Reporting Name

JAK2 Exon 12-15 Sequencing, Reflex

Specimen Type

Varies

Specimen Minimum Volume

Blood, Bone marrow: 0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Varies Refrigerated (preferred) 5 days
  Ambient  5 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

NA

Icterus

NA

Other

Paraffin embedded bone marrow aspirate clot or biopsy blocks, slides, paraffin shavings, heparin, moderately to severely clotted

Clinical 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. The JAK2 V617F is located in exon 14 and present in 50% to 60% of primary myelofibrosis and essential thrombocythemia, and 95% to 98% of polycythemia vera (PV). In the rest of the polycythemia vera cases, over 50 different mutations have been reported within exons 12 through 15 of JAK2 and essentially all of the non-V617F JAK2 mutations have been identified in polycythemia vera. These mutations include point mutations 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 requires further clinical and research evaluation.

Reference Values

Only orderable as a reflex. For more information, see PVJAK / Polycythemia Vera, JAK2 V617F with Reflex to JAK2 Exon 12-15, Sequencing for Erythrocytosis.

Interpretation

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.

Cautions

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.

Method Description

Genomic RNA is extracted.

 

For the Sanger sequencing, total RNA is extracted from whole blood/bone marrow and cDNA synthesized from JAK2 mRNA. A fragment spanning exons 12 through 15 is then amplified using standard PCR and the sequence obtained using Sanger sequencing (BigDye terminator V1.1 cycle sequencing kit from Applied Bioscience) with analysis on an automated genetic analyzer.(Applied Biosystems 3130; Unpublished Mayo method)

Day(s) and Time(s) Performed

Monday through Friday

Analytic Time

7 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

0027U-JAK2 (Janus kinase 2) (eg, myeloproliferative disorder), exon 12 sequence and exon 13 sequence, if performed