Test ID: JAK2B
JAK2 V617F Mutation Detection, Blood
NY State Approved 
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Aiding in the distinction between a reactive cytosis and a chronic myeloproliferative disorder
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
The following algorithms are available in Special Instructions:
-Erythrocytosis Evaluation Testing Algorithm
-Myeloproliferative Neoplasm: A Diagnostic Approach to Peripheral Blood Evaluation
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Point Mutation Detection in DNA Using Quantitative Polymerase Chain Reaction (PCR)
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
83872-JAK2B
Tyrosine Kinase Mutation
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Specimen must arrive within 96 hours of draw.
Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: ACD
Specimen Volume: 4 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send specimen in original tube.
Forms:
1. Hematopathology Patient Information Sheet (Supply T676) in Special Instructions
2. If not ordering electronically, please submit a Hematopathology/Molecular Oncology Request Form (Supply T241) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Whole Blood EDTA | Ambient (preferred) | 4 days |
| Refrigerated | 4 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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. Receptor binding by extracellular ligand causes receptor multimerization and brings JAK2 proteins together to allow activation by transphosphorylation. Activated JAK2 then phosphorylates the cytoplasmic portion of the receptor creating a docking site for the latent transcription factor, STAT5, which is also phosphorylated by JAK2. Phosphorylated STAT5 then forms dimers that translocate into the nucleus and initiate transcription of genes ultimately responsible for cell growth and differentiation.
Recently, a point mutation in JAK2 (V617F) was identified in the hematopoietic cells of several chronic myeloproliferative disorders (CMPDs), most frequently polycythemia vera (65%-97%), essential thrombocythemia (25%-55%), and chronic idiopathic myelofibrosis (35%-57%).(1-3) The mutation has been reported at much lower frequency in some other CMPDs, chronic myelomonocytic leukemia and myelodysplastic syndromes.(4) It has not been reported in chronic myelogenous leukemia (CML), normal patients, or reactive cytoses.(1-4) This mutation causes constitutive activation of JAK2 and is thought to play a key role in the neoplastic phenotype. Since it is often difficult to distinguish reactive conditions from the non-CML CMPDs, identification of the JAK2 mutation has diagnostic value. Potential prognostic significance of JAK2 mutation detection in chronic myeloid disorders has yet to be clearly established.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
An interpretive report will be provided.
Interpretation Provides information to assist in interpretation of the test results
The results will be reported as 1 of the 3 states:
-Negative for JAK2 V617F mutation
-Below the laboratory cutoff for JAK2 V617F mutation positivity
-Positive for JAK2 V617F mutation
Positive mutation status is highly suggestive of a myeloid neoplasm, but must be correlated with clinical and other laboratory features for definitive diagnosis. Negative mutation status does not exclude the presence of a chronic myeloproliferative disorder or other neoplasm. Results below the laboratory cutoff for positivity are of unclear clinical significance at this time.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
A positive result is not specific for a particular diagnosis and clinicopathologic correlation is necessary in all cases.
A negative result does not exclude the presence of a chronic myeloproliferative disorder or other neoplastic process.
In rare cases, a mutation other than the V617F may be present in an area that interferes with primer or probe binding and cause a false negative result.
Supportive Data
Analytical sensitivity is at least 0.001% (positively detected in 5 log dilutions of positive cell line or positive patient DNA into negative DNA) as assessed by positive cell line and patient samples dilution experiments. Clinical sensitivity and specificity appear close to 100% based on all available data.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
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
Method Description Describes how the test is performed and provides a method-specific reference
Genomic DNA is extracted and 2 PCR reactions are used for each sample. In each reaction, a short fragment of genomic DNA, including the mutation site, is amplified using quantitative PCR in a real-time PCR instrument (LightCycler 480, Roche). In 1 reaction, the 5' terminal base of the reverse primer matches the mutated sequence and the PCR conditions are such that it will only bind mutated DNA. In the second reaction, the 5' terminal base of 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 mutated DNA and the amount of wild-type DNA is measured for each sample. In each run, the amount of mutated and wild-type DNA in a calibrator DNA sample is also measured. The calibrator is a mixture of DNA from a positive cell line (HEL) and a negative cell line (HL60) that is frozen in aliquots and expected to give an identical result in each run. Deviations in the calibrator result are assumed to be due to deviations in the run conditions and the sample results are corrected accordingly. Following each reaction, LightCycler 480 Relative Quantification Software is used to calculate the mutated:wild-type ratio, which is expressed as a unitless normalized ratio following correction with the calibrator data.
The formula for the normalized ratio is as follows:
| Normalized ratio = | mutated/wild-type (sample) |
| mutated/wild-type (calibrator) |
Samples with a normalized ratio of 0 are considered negative.
Samples with a normalized ratio of <1x10(2) are considered below the cutoff level for positivity.
Samples with a normalized ration of > or =1x10(2) are considered positive.
(Instruction manual: Roche Applied Science Technical Note No. LC 13/2001. Relative Quantification; LightCycler 480, 2006)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 12 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
81270-JAK2 (Janus kinase 2) (eg, myeloproliferative disorder) gene analysis, p.Val617Phe (V617F) variant
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 29590 | JAK2 V617F Mutation Detection, B | 43399-5 |
| 31132 | Method: | 49549-9 |
| 31133 | Reviewed By: | In Process |
| 31073 | HPGDE, DNA Extraction | N/A |
| 31074 | Interpretation and Report | In Process |
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