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Common Mayo Medical Laboratories Test-Ordering Errors
Part 4: Overordered Tests

JAK2 on Blood and Bone Marrow
Free Thyroxine index (FTI) and T3 Uptake


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JAK2 Gene

Slide 5

July 2010

Let’s look at JAK2 as an example.  The gene JAK2 encodes for a tyrosine kinase (called Janus kinase 2, also abbreviated JAK2). The JAK2 protein is involved in growth and differentiation of hematopoietic cells.  A specific mutation in JAK2 (named V617F) is present in the hematopoietic cells of several chronic myeloproliferative disorders, most frequently in polycythemia vera, where it is present in approximately 90% of cases. If this mutation is present, it can be identified using either blood cells obtained by venipuncture or cells obtained by bone marrow aspiration—there is no need to order both tests. In fact, because of its high-negative predictive value (that is, its ability to rule-out polycythemia if not present), some have advocated use of the JAK2 test in peripheral blood as a means of eliminating the need for bone marrow biopsy in patients with clinical or lab features consistent with polycythemia vera. We are unclear why we receive dual orders as we assume that it is well known that a genetic marker present in blood cell precursors in bone marrow cells will also be present in those cells in the peripheral blood. We can only speculate that the tests are ordered at different times or by different physicians who are unaware of previous orders. Review of orders for duplicates prior to sending the request could resolve this problem.

JAK2 Gene


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