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EPIC ORDER CODE LAB2568 JAK2 V617F Mutation Detection, Blood

Additional Codes

SQ: JAK2DB

Reporting Name

JAK2 V617F Mutation Detection, B

Useful For

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

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole Blood EDTA


Shipping Instructions


Specimen must arrive within 7 days of collection.



Specimen Required


Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD)

Specimen Volume: 4 mL

Collection Instructions:

1. Invert several times to mix blood.

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


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood EDTA Ambient (preferred) 7 days PURPLE OR PINK TOP/EDTA
  Refrigerated  7 days PURPLE OR PINK TOP/EDTA

Reference Values

An interpretive report will be provided.

Day(s) Performed

Monday through Saturday

CPT Code Information

81270-JAK2 (Janus kinase 2) (eg, myeloproliferative disorder) gene analysis, p.Val617Phe (V617F) variant

LOINC Code Information

Test ID Test Order Name Order LOINC Value
JAK2B JAK2 V617F Mutation Detection, B 43399-5

 

Result ID Test Result Name Result LOINC Value
39722 JAK2 Result 53761-3
29590 JAK2 V617F Mutation Detection, B 43399-5

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. 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 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 an 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.

Interpretation

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

-Negative for JAK2 V617F variant

-Positive for JAK2 V617F variant

 

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.

Clinical Reference

1. Baxter EJ, Scott LM, Campbell PJ, et al. Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders. Lancet. 2005;365(9464):1054-1061

2. James C, Ugo V, Le Couedic JP, et al. A unique clonal JAK2 mutation leading to constitutive signaling causes polycythaemia vera. Nature. 2005;434(7037):1144-1148

3. Kralovics R, Passamonti F, Buser AS, et al. A gain-of-function mutation of JAK2 in myeloproliferative disorders. N Engl J Med. 2005;352:1779-1790

4. Steensma DP, Dewald GW, Lasho TL, et al. The JAK2 V617F activating tyrosine kinase mutation is an infrequent event in both "atypical" myeloproliferative disorders and the myelodysplastic syndrome. Blood. 2005;106:1207-1209

5. Gong, Jerald Z, Cook, James R, et al. Laboratory practice guidelines for detecting and reporting JAK2 and MPL mutations in myeloproliferative neoplasms. J Mol Diag. 2013;15(6):733-744

6. Stuckey R, Gomez-Casares MT. Recent advances in the use of molecular analyses to inform the diagnosis and prognosis of patients with polycythaemia vera. Int J Mol Sci. 2021;22(9):5042. doi:10.3390/ijms22095042

Method Description

Genomic DNA is extracted, and 2 polymerase chain reaction (PCR) amplifications are used for each sample. In each reaction, a short fragment of genomic DNA, including the variant site, is amplified using quantitative PCR in a real-time PCR instrument. In the first reaction, the 5' terminal base of the reverse primer matches the mutated sequence, and the PCR conditions are such that it will only bind mutated DNA. In the second reaction, the 5' terminal base of the reverse primer matches the wild-type sequence, and the PCR conditions are such that it will only bind the wild-type sequence. In both reactions, the PCR is monitored using TaqMan probe chemistry. The amount of mutated DNA and the amount of wild-type DNA is measured for each sample. In each run, the amount of mutated and wild-type DNA in a calibrator DNA sample is also measured. The calibrator is a mixture of DNA from a positive cell line (HEL) and a negative cell line (HL60) that is frozen in aliquots and expected to give an identical result in each run. Deviations in the calibrator result are assumed to be due to deviations in the run conditions and the sample results are corrected accordingly. Following each reaction, Relative Quantification Software is used to calculate the normalized mutated:wild-type ratio, which is expressed as a unitless ratio following correction with the calibrator data.

 

The formula for the normalized ratio is as follows:

 

Normalized ratio =

mutated/wild type (sample)

mutated/wild type (calibrator)

 

The final result is reported as percent JAK2 V617F of total JAK2 (ie, [mutated/mutated + wild type] x 100%) calculated from the normalized mutated:wild-type ratio.(Unpublished Mayo method)

Report Available

2 to 5 days

Specimen Retention Time

Whole blood: 2 weeks; Extracted DNA: 3 months

Reject Due To

Gross hemolysis Reject
Moderately to severely clotted Reject

Test Classification

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

Method Name

Quantitative Polymerase Chain Reaction (PCR)

Forms

1. Hematopathology Patient Information (T676)

2. If not ordering electronically, complete, print, and send a Hematopathology/Cytogenetics Test Request (T726) with the specimen.