The diagnosis of polycythemia vera: New tests and old dictums

Pathogenetically fundamental observations have identified polycythemia vera (PV) as a clonal stem cell disease with bone marrow histological and other biological features that distinctly differentiate it from other causes of ‘increased’ hematocrit. However, relatively little attention has been given to the effective utilization of pathology and laboratory markers of clonal myeloproliferation as diagnostic tools in PV. In contrast, the diagnostic use of red cell mass (RCM) measurement in PV stemmed from the accidental endorsement, as ‘diagnostic criteria’, of ‘study eligibility criteria’ that were formulated for clinical trials. It has since become evident that RCM measurement is a tedious procedure that is fraught with multiple-level imprecision, as well as suboptimal diagnostic accuracy. Therefore, it is reasonable to consider dispensing with RCM measurement as a diagnostic test for PV and instead utilize a diagnostic algorithm that combines clinical information with easily accessible laboratory data, including serum erythropoietin level and bone marrow histology. Recent discoveries of myeloproliferative-disease-specific molecular markers, including the JAK2 V617F tyrosine kinase mutation that is found in the majority of patients with PV, provide further support for such a measure.