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Test Code LABJAKXB JAK2 Exon 12 and Other Non-V617F Mutation Detection, Blood

Additional Codes

Test Name in EPIC EPIC Test Code Mnemonic Mayo Test ID
JAK2 EXON 12 MUTATION DETECTION LABJAKXB JAKXB JAKXB

 

Reporting Name

JAK2 Exon 12 Mutation Detection, B

Useful For

Second-order testing to aid in the distinction between a reactive cytosis and a myeloproliferative neoplasm, particularly when a diagnosis of polycythemia is being entertained; for use with blood specimens

Testing Algorithm

This is a second-order test that should be used when the test for the JAK2B / JAK2 V617F Mutation Detection, Blood test is negative. The sensitivity of this assay is much less than that of the JAK2B blood test. This is because the sequencing technique is required to evaluate for many potential mutations. The sensitive JAK2B blood test should always be performed first, as the JAK2 mutation burden may be very low in some specimens. If JAK2B blood test is negative, then this assay (JAKXB / JAK2 Exon 12 and Other Non-V617F Mutation Detection, Blood) should be performed for detection of non-V617F JAK2 mutations.

 

The following algorithms are available in Special Instructions:

-Myeloproliferative Neoplasm: A Diagnostic Approach to Peripheral Blood Evaluation

-Erythrocytosis Evaluation Testing Algorithm

Method Name

Mutation Detection in cDNA Using Sanger Sequencing

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Whole blood


Advisory Information


The sensitivity of this assay is much less than that of JAK2B / JAK2 V617F Mutation Detection, Blood. This is because the sequencing technique is required to evaluate for many potential mutations. The sensitive JAK2B / JAK2 V617F Mutation Detection, Blood should always be performed first, as the JAK2 mutation burden may be very low in some specimens. If JAK2B / JAK2 V617F Mutation Detection, Blood is negative, then this assay, JAKXB / JAK2 Exon 12 and Other Non-V617F Mutation Detection, Blood, should be performed for detection of non-V617F JAK2 mutations.



Additional Testing Requirements


 



Shipping Instructions


Specimen must arrive within 5 days (120 hours) of collection. Draw and package specimen as close to shipping time as possible.



Necessary Information


Date of collection is required.



Specimen Required


Container/Tube:

Preferred: EDTA (lavender top)

Acceptable: ACD (yellow top)

Specimen Volume: 4 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Refrigerated (preferred) 5 days
  Ambient  5 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

NA

Icterus

NA

Other

Moderately to severely clotted

 

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Monday through Friday

CPT Code Information

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
JAKXB JAK2 Exon 12 Mutation Detection, B In Process

 

Result ID Test Result Name Result LOINC Value
39467 JAK2 Sequencing Result No LOINC Needed
20194 Final Diagnosis: 34574-4

Analytic Time

5 days

Cautions

A positive result is not specific for a particular diagnosis and clinico-pathologic correlation is necessary in all cases. A negative result does not exclude the presence of a myeloproliferative or other neoplasm.

 

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 approximately 20% meaning there must be about 20% of the mutated DNA in the sample for reliable detection.

Method Description

Total RNA is extracted from whole blood 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.(Package insert: Applied Biosystems 3130; unpublished Mayo method)

Interpretation

The results will be reported as 1 of 2 states:

1. Negative for JAK2 mutation

2. Positive for JAK2 mutation

 

If the result is positive, a description of the mutation at the nucleotide level and the altered protein sequence is reported.

 

Positive mutation status is highly suggestive of a myeloproliferative neoplasm, but must be correlated with clinical and other laboratory features for a definitive diagnosis. Negative mutation status does not exclude the presence of a myeloproliferative or other neoplasm.

Specimen Retention Time

RNA 1 year

Clinical Information

DNA sequence mutations in the Janus kinase 2 gene (JAK2) are found in the hematopoietic cells of several myeloproliferative neoplasms (MPNs), most frequently polycythemia vera (close to 100%), essential thrombocythemia (approximately 50%), and primary myelofibrosis (approximately 50%). Mutations in JAK2 have been reported at much lower frequency in other MPNs, chronic myelomonocytic leukemia and mixed MPN/myelodysplastic syndromes, but essentially never in chronic myelogenous leukemia (CML), reactive cytoses, or normal patients. Mutations are believed to cause constitutive activation of the JAK2 protein, which is an intracellular tyrosine kinase important for signal transduction in many hematopoietic cells. Since it is often difficult to distinguish reactive conditions from the non-CML MPNs, identification of a JAK2 mutation has diagnostic value. Potential prognostic significance of JAK2 mutation detection in chronic myeloid disorders has yet to be clearly established.

 

The vast majority of JAK2 mutations occur as base pair 1849 in the gene, resulting in a JAK2 V617F protein change. In all cases being evaluated for JAK2 mutation status, the initial test that should be ordered is JAK2B / JAK2 V617F Mutation Detection, Blood, a sensitive assay for detection of the mutation. However, if no JAK2 V617F mutation is found, further evaluation of JAK2 may be clinically indicated. Over 50 different mutations have now been reported within exons 12 through 15 of JAK2 and essentially all of the non-V617F 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, research in this area is ongoing.

 

This assay for non-V617F/alternative JAK2 mutations is designed to obtain the sequence for JAK2 exons 12 through the first 90% of exon 15, which spans the region containing all mutations reported to date.

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.

Forms

1. Hematopathology Patient Information (T676) in Special Instructions

2. If not ordering electronically, complete, print, and send a Hematopathology/Cytogenetics Test Request Form (T726) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/hematopathology-request-form.pdf).