JAK2 V617F mutation testing in polycythemia vera: use and impact in an academic practice.

Background: The observation that a mutation in JAK2 (JAK2 V617F) is present in more than 90% of cases of polycythemia vera (PV) has altered the diagnostic approach to this disease. However, most studies of the utility of JAK2 V617F have been performed in large PV populations; most hematologists or hematologist-oncologists have relatively few PV patients in their individual practices.

Approach: To assess its impact in a practice of more typical size, the use of JAK2 V617F testing was reviewed in 5 individual clinics in an academic practice after a total of 16 patients carrying an established or presumed diagnosis of PV.

Results: Nine patients were tested for JAK2 V617F mutation. The majority (6 of 9) were tested near diagnosis. Two of the 3 established patients tested did not meet PV diagnostic criteria fully. Most patients not tested met World Health Organization criteria for PV. Of the 9 patients tested, 7 had a mutation detected (5 tested at diagnosis). Results of mutation testing changed the diagnosis in 2 cases.

Conclusions: In a PV population similar in size to what an individual or small group practice might follow, JAK2 V617F mutation testing was primarily used in the early evaluation of suspected PV. Mutation testing was infrequently used in continuing patients where the physician considered the diagnosis clearly established or where a change in diagnosis would not alter management.