Primary polycythaemia: diagnosis by non‐conventional positive criteria

Patients with polycythaemia and normal controls have been studied to establish and subsequently test non‐conventional criteria for the diagnosis of primary polycythaemia (primary proliferative polycythaemia, polycythaemia vera) as compared with conventional Polycythaemia Vera Study Group (PVSG) assessment. One criterion was erythroid colony formation from peripheral blood in a serum‐free system, assayed alone and with the addition of recombinant human erythropoietin (Epo), interleukin 3 (IL3), or α interferon (α‐IFN) (Dudley et al. 1990). The remaining criteria were non‐culture associated and comprised platelet distribution width (PDW), platelet nucleotide ratio (ATP:ADP), serum erythropoietin and clinical evidence of ischaemic vascular disease. The combination of culture associated and non‐culture associated variables, by use of a simple additive scoring system, gave no false positive and only 6% false negative results in distinguishing primary polycythaemia from other polycythaemias and normal controls in those (34 patients Group A) used in its derivation. Testing the scoring system in a newly presenting group (25 patients Group B) was highly satisfactory with no false positives and only a few false negative results (14%). Use of these non‐conventional criteria should allow more confident diagnosis of primary polycythaemia, where conventional clinical and laboratory assessment is inconclusive.