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Test ID: MPNR Myeloproliferative Neoplasm, JAK2 V617F with Reflex to CALR and MPL, Varies

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

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

Reporting Name

MPN (JAK2 V617F, CALR, MPL) Reflex

Specimen Type


Shipping Instructions

Specimen must arrive within 7 days of collection.

Necessary Information

The following information is required:

1. Pertinent clinical history

2. Clinical or morphologic suspicion

3. Date of collection

4. Specimen source

Specimen Required

Submit only 1 of the following specimens:


Specimen Type: Blood

Container/Tube: Lavender top (EDTA) or yellow top (ACD solution B)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

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

3. Label specimen as blood.

Specimen Stability Information: Ambient (preferred)/Refrigerate


Specimen Type: Bone marrow

Container/Tube: Lavender top (EDTA) or yellow top (ACD solution B)

Specimen Volume: 2 mL

Collection Instructions:

1. Invert several times to mix bone marrow.

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

3. Label specimen as bone marrow.

Specimen Stability Information: Ambient (preferred)/Refrigerate


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

Specimen Minimum Volume

Blood and Bone marrow: 0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies 7 days

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.

Reference Values

An interpretive report will be provided.


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 Reference

1. Baxter EJ, Scott LM, Campbell PJ, et al: Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders. Lancet 2005 March 16;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 April 28;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. Klampfl T, Gisslinger H, Harutyunyan AS, et al: Somatic mutation of calreticulin in myeloproliferative neoplasms. N Engl J Med 2013;369:2379-2390

6. Nangalia J, Massie CE, Baxter EJ, et al: Somatic CALR mutation in myeloproliferative neoplasms with nonmutated JAK2. N Engl J Med 2013;369:2391-2405

7. Pikman Y, Lee BH, Mercher T, et al: MPLW515L is a novel somatic activating mutation in myelofibrosis with myeloid metaplasia. PLoS Med 2006;3:e270

8. Pardanani A, Levine R, Lasho T, et al: MPL515 mutations in myeloproliferative and other myeloid disorders: a study of 1182 patients. Blood 2006;108:3472-3476

9. Kilpivaara O, Levine RL: JAK2 and MPL mutations in myeloproliferative neoplasms: discovery and science. Leukemia 2008;22:1813-1817

Day(s) Performed

Monday through Friday

Report Available

7 to 10 days

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 US Food and Drug Administration.

CPT Code Information

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)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MPNR MPN (JAK2 V617F, CALR, MPL) Reflex In Process


Result ID Test Result Name Result LOINC Value
39725 MPNR Result No LOINC Needed
36687 Final Diagnosis 22637-3

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

Method Name

Quantitative Polymerase Chain Reaction (qPCR)


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

Mayo Clinic Laboratories | Hematology Catalog Additional Information: