Evaluation of diagnostic criteria in polycythemia vera

Abstract

There is no single diagnostic marker for the only known type of primary acquired erythrocytosis, polycythemia vera (PV). The Polycythemia Vera Study Group (PVSG) used a combination of major and minor diagnostic criteria. However, these guidelines have some limitations and in the presence of newer diagnostic tools, have been re-evaluated. The recommendations of the Radionuclide Panel of the International Council for Standardization Hematology based on surface area are recommended over red blood cell mass (RCM) mL/kg expressions. Absolute erythrocytosis can be assumed in males and females with packed cell volume (PCV) values greater than 0.60 and greater than 0.56, respectively. A satisfactory strategy of investigation for a secondary erythrocytosis must be used. Hypoxemia, as well as renal and hepatic pathology, must be excluded. In unexplained absolute erythrocytoses, pO 2 50 values and serum erythropoietin (EPO) levels should be examined. The latter can be disappointing in the confirmation of a secondary erythrocytosis, but elevated values contraindicate a diagnosis of a primary erythrocytosis. Establishment of a clonal marrow population supports a diagnosis of PV. Thus an acquired karyotypic abnormality is a major criterion. Palpable splenomegaly remains an important diagnostic marker. Scanning techniques to demonstrate splenic enlargement should be used with caution. Allowance must be made for interobserver and intraobserver differences and variation in normal spleen size with age and size of the subject. Splenomegaly demonstrated in this way should be taken as a minor criterion. An increased neutrophil count (> 10 × 10 9/L. and > 12.5 × 10 9/L. in smokers) is readily measurable and should replace total white blood cell count. The error in measurement of neutrophil alkaline phosphatase (NAP) score is large, making it an unsuitable diagnostic criterion. Neutrophil and platelet counts (> 400 × 10 9/L) should be taken as separate minor criteria. Endogenous erythroid colonies (EEC) grown from the peripheral blood have been used as a marker of PV, but it is an expensive technique that is not standardized and not totally specific for PV. Low serum EPO values found in the majority of patients with PV should hold a linked minor criterion position with EEC. Expert opinions should be obtained if bone marrow histology is to be used in the diagnosis of PV, but histology holds an important role in confirming the diagnosis.