Myeloproliferative Neoplasm, JAK2 V617F with Reflex to CALR and MPL, Varies

Message

The following information is required:

Pertinent clinical history
Clinical or morphologic suspicion
Date of collection
Specimen source

Test Code

MPNR

Alias/See Also

Epic: LAB14057
Mayo: MPNR

83872-JAK2B
Janus kinase 2 gene
Tyrosine Kinase Mutation
CALR
Calreticulin
Essential Thrombocythemia
JAK2-negative Myeloproliferative Neoplasm
Myelofibrosis
Myeloproliferative Disorder
Myeloproliferative Neoplasm (MPN)
Primary Myelofibrosis
MPL S505
MPLW515
Myeloproliferative leukemia virus oncogene

CPT Codes
81270-JAK2 (Janus kinase 2) (eg, myeloproliferative disorder) gene analysis, p.Val617Phe (V617F) variant 81219-CALR (calreticulin) (eg, myeloproliferative disorders), gene analysis, common variants in exon 9 (if appropriate) 81339-MPL (MPL proto-oncogene, thrombopoietin receptor) (eg, myeloproliferative disorder) gene analysis; sequence analysis, exon 10 (if appropriate)

Includes

REFLEX TESTS

Test Id	Reporting Name	Available Separately	Always Performed
CALX	CALR, Gene Mutation, Exon 9, Reflex	No, (bill only)	No
MPLR	MPL Exon 10 Mutation Detection, R	No, (bill only)	No

TESTING ALGORITHM

This reflex test sequentially evaluates for the common major gene variants associated with non-BCR-ABL1-positive myeloproliferative neoplasms until a variant is identified. The testing sequence is based on the reported frequency of gene variants in this disease group. Initial testing evaluates for the presence of the JAK2 V617F variant. If this result is negative or very low positive (0.06%-0.6%), testing proceeds with assessment for CALR gene variants. If the CALR result is also negative, then testing proceeds to evaluate for variants in exon 10 of the MPL gene. If either JAK2 V617F (>0.6%) or CALR variants are detected in the process, the testing algorithm ends; therefore, the complete reflex is followed only in the event of sequential negative variant. An integrated report is issued with the summary of test results.

The following algorithms are available in Special Instructions:
-Myeloproliferative Neoplasm: A Diagnostic Approach to Bone Marrow Evaluation
-Myeloproliferative Neoplasm: A Diagnostic Approach to Peripheral Blood Evaluation

Preferred Specimen

Submit only 1 of the following specimens:

Specimen Type: Whole blood EDTA
Collection Container: Lavender top (EDTA)
Specimen Volume: 3 mL

Specimen Type: Bone marrow

Collection Container: Lavender top (EDTA)

Specimen Volume: 2 mL

Minimum Volume

0.5 mL

Other Acceptable Specimens

Specimen Type: Extracted DNA from blood or bone marrow
Container/Tube: 1.5- to 2-mL tube
Specimen Volume: Entire specimen
Collection Instructions: Label specimen as extracted DNA from blood or bone marrow and provide indication of volume and concentration of the DNA.
Specimen Stability Information: Frozen (preferred)/Refrigerate/Ambient

Instructions

Invert several times to mix blood.
Send specimen in original tube. Do not aliquot.
Label specimen as blood.

Transport Container

Send specimen in original tube. Do not aliquot.

Specimen Stability

Specimen Type	Temperature	Time	Special Container
Varies	Varies	7 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Gross hemolysis	Reject
Paraffin-embedded bone marrow aspirate clot or biopsy blocks Slides Paraffin shavings Moderately to severely clotted

Methodology
Quantitative Polymerase Chain Reaction (qPCR)

Setup Schedule

Monday through Friday

Report Available

7 to 10 days

Limitations

CAUTIONS
A positive result is not specific for a particular subtype of myeloproliferative neoplasm and clinicopathologic correlation is necessary in all cases.

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

In rare cases, a variant other than JAK2 V617F may be present in an area that interferes with primer or probe binding, which may cause a false-negative result.

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.

SUPPORTIVE DATA
Analytical sensitivity is determined at 0.06% (by dilution of a JAK2 V617F-positive cell line into a negative cell line DNA).

Reference Range

REFERENCE VALUES
An interpretive report will be provided.

INTERPRETATION
The results will be reported as 1 of the 4 following states:

-Positive for JAK2 V617F variant
-Positive for CALR variant
-Positive for MPL variant
-Negative for JAK2 V617F, CALR, and MPL variants

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 neoplasms.

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

Clinical Significance

USEFUL FOR
Aiding in the distinction between a reactive cytosis and a chronic myeloproliferative disorder

Evaluating for variants in JAK2, CALR, and MPL genes in an algorithmic process

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). JAK2 V617F is present in 95% to 98% of polycythemia vera (PV), and 50% to 60% of primary myelofibrosis (PMF) and essential thrombocythemia (ET). It has also been described infrequently in other myeloid neoplasms, including chronic myelomonocytic leukemia and myelodysplastic syndrome. Detection of JAK2 V617F is useful to help establish the diagnosis of MPN. However, a negative JAK2 V617F result does not indicate the absence of 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). Variants in JAK2, CALR, and MPL are essentially mutually exclusive. A CALR variant is associated with decreased risk of thrombosis in both ET and PMF and confers a favorable clinical outcome in PMF patients. A triple negative (JAK2 V617F, CALR, and MPL-negative) genotype is considered a high-risk molecular signature in PMF.

Performing Laboratory
Mayo Clinic Laboratories - Rochester
3050 Superior Drive NW
Rochester, MN 55901

Last Updated: December 27, 2023
Last Review: N. Wolford, December 27, 2023

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.