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Test ID JAKXB JAK2 Exon 12 and Other Non-V617F Mutation Detection, Blood

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

Method Name

Mutation Detection in cDNA Using Sanger Sequencing

Reporting Name

JAK2 Exon 12 Mutation Detection, B

Specimen Type

Whole blood

Ordering Guidance

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.

Additional Testing Requirements


Shipping Instructions

1. Specimen must arrive within 5 days (120 hours) of collection.

2. Draw and package specimen as close to shipping time as possible.

Necessary Information

Date of collection is required.

Specimen Required


Preferred: EDTA (lavender top)

Acceptable: ACD (yellow top)

Specimen Volume: 10 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Minimum Volume

4 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Refrigerated (preferred) 5 days PURPLE OR PINK TOP/EDTA
  Ambient  5 days PURPLE OR PINK TOP/EDTA

Reference Values

An interpretive report will be provided.

Day(s) Performed

Monday through Friday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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 55300-8


Result ID Test Result Name Result LOINC Value
39467 JAK2 Sequencing Result 55300-8
20194 Final Diagnosis: 34574-4

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.

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 test. This is because the sequencing technique is required to evaluate for many potential mutations. The sensitive JAK2B test should always be performed first, as the JAK2 mutation burden may be very low in some specimens. If the JAK2B test is negative, then this assay 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

Report Available

5 to 8 days

NY State Approved



1. Hematopathology Patient Information (T676) in Special Instructions

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