In Reply All JAK2 testing, whether quantitative or qualitative, is performed on blood or bone marrow specimens and not plasma, as Drs Reeves and Gulley correctly state. The function of JAK2 in cytokine signal transduction and cellular transport limits its presence to blood cellular elements.1 The results of JAK2V617F testing from marrow or blood are typically reported either qualitatively (mutation present or absent [negative]) or quantitatively as an allele burden (% JAK2V617F of total JAK2; ie, [mutated/mutated + wild-type] × 100%). The sentence in our original article—“Typically, JAK2V617F is quantitatively reported as pictogram of JAK2V617F per microliter of plasma (Medicare reimbursement cost of testing, $124.87), although qualitative tests are available.”—was incorrect. It should have read: “Typically, JAK2V617F is quantitatively reported as a percentage of extracted genomic DNA found to have the point mutation causing JAK2V617F (Medicare reimbursement cost of testing, $124.87), although qualitative tests are available.” The article has been corrected online.
Scherber RM, Mesa RA. Evaluating Elevated Hemoglobin—Reply. JAMA. 2016;316(10):1115. doi:10.1001/jama.2016.11335