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HelpTest Code 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%-2%), 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 (>2%) 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.
For more information the following algorithms are available:
-Myeloproliferative Neoplasm: A Diagnostic Approach to Bone Marrow Evaluation
-Myeloproliferative Neoplasm: A Diagnostic Approach to Peripheral Blood Evaluation
Special Instructions
Reporting Name
MPN (JAK2 V617F, CALR, MPL) ReflexSpecimen Type
VariesShipping 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: Whole 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 whole blood specimen in original tube. Do not aliquot.
3. Label specimen as blood.
Specimen Stability Information: Ambient (preferred)/Refrigerate 7 days
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 bone marrow specimen in original tube. Do not aliquot.
3. Label specimen as bone marrow.
Specimen Stability Information: Ambient (preferred)/Refrigerate 7 days
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, bone marrow: 0.5 mL; Extracted DNA: 50 mcL at 20 ng/mcL concentration
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Varies | 7 days |
Reject Due To
| Gross hemolysis | Reject |
| Paraffin-embedded bone marrow aspirate clot or biopsy blocks Slides Paraffin shavings Moderately to severely clotted |
Reject |
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).
The JAK2 V617F variant is present in 95% to 98% of patients with polycythemia vera, 50% to 60% of patients with primary myelofibrosis (PMF), and 50% to 60% of patients with essential thrombocythemia (ET). It has also been described infrequently in other myeloid neoplasms, including chronic myelomonocytic leukemia and myelodysplastic syndrome. Detection of JAK2 V617F helps 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 patients with PMF. 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.
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 currently.
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.
Method Description
Genomic DNA is extracted, and 2 polymerase chain reaction (PCR) reactions 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 one reaction, the reverse primer matches the altered sequence, and the PCR conditions are such that it will only bind altered DNA. In the second reaction, 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 altered DNA and the amount of wild-type DNA is measured for each sample. In each run, the amount of altered and wild-type DNA in a calibrator DNA sample is also measured.
The final result is reported as % JAK2 V617F of total JAK2.(Unpublished Mayo method)
Day(s) Performed
Monday through Friday
Report Available
7 to 10 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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.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)