The UIHC Molecular Pathology Laboratory announces the implementation of a new molecular diagnostics test to detect the presence of the G^_>T transversion in the Janus kinase 2 (JAK2) gene resulting in a Valine-to-Phenylalanine substitution at position 617 of JAK2 (JAK2 V617F). The JAK2 V617F somatic mutation is found in nucleated myeloid cells and erythrocytic precursors of patients with non-CML myeloproliferative syndromes, including polycythemia vera (PV; >90%), essential thrombocythemia (ET; ~50%) and chronic idiopathic myelofibrosis (CIMF; 35-60%)^1-3. This mutation is rarely present in myelodysplastic syndromes (≤5%), chronic myelomonocytic leukemia (<5%), and acute myeloid leukemia (≤2%), which may reflect a low but detectable mutation frequency among otherwise healthy persons^4,5. It has not been reported in chronic myeloid leukemia (CML), acute lymphoblastic or chronic lymphocytic leukemia (ALL or CLL), or lymphomas.

This test is most helpful to confirm a diagnosis of PV in patients with increased red cell mass and a low serum erythropoietin level; it has a reasonably high negative predictive value for PV to rule out this diagnosis. The presence of JAK2 V617F is also useful in the diagnosis of ET or CIMF when other clinically similar conditions have been ruled out (e.g., reactive thrombocytosis), but the negative predictive values are too low to rule out these clinical entities. Importantly, the presence of the JAK2 V617F mutation does not obviate the need to perform bone marrow biopsy for any of these myeloproliferative syndromes³.

The UIHC JAK2 V617F mutation detection test relies on allele-specific PCR and separation of fluorescently labeled products by capillary electrophoresis. Both wild-type and mutant JAK2 alleles are amplified from high-quality genomic DNA prepared from peripheral blood, bone marrow, or purified granulocytes. It may also be performed on DNA processed from certain fixed, paraffin-embedded tissues. The presence of both PCR products, or of only a single correctly sized mutant product, indicates that nucleated cells harboring the JAK2 V617F mutation were present in the sample. This assay has a detection limit of 0.1% or less (highly sensitive), and is ~100% specific for the JAK2 V617F allele, as determined by the UIHC Molecular Pathology Laboratory.

The JAK2 V617F mutation detection assay is performed weekly; results are usually reported within 5 business days or less (rarely, repeat testing may be required that could delay reporting). The test determines a qualitative presence or absence of the mutation only. Please use XX requisition forms when ordering the JAK2 V617F mutation detection test. For further information, please contact Jon Heusel, MD, PhD (335-8217/jon-heusel@uiowa.edu) or the Molecular Pathology laboratory (354-9568/BT 6004 GH).

References
1. Kralovics et al. (2005) N Engl J Med 352(17):1779-90.
2. Tefferi A et al. (2006) Cancer 106(3):631-5.
3. Tefferi A and Pardanani A. (2006) Leukemia Res 30(6):739-44.
4. Steensma DP et al. (2005) Blood 106:1207-09.
5. Sidon P, et al. (2006) Leukemia [E Pub ahead of print].