PRIMARY THROMBOCYTHEMIA - A COMPOSITE APPROACH TO DIAGNOSIS

Traditional diagnostic criteria for primary thrombocythaemia (PT) rema in essentially negative, aiming to exclude other myeloproliferative di sorders and causes of reactive thrombocytosis (RT). It would be useful to have positive markers. We have examined several parameters to see how well they discriminate between PT and RT. Three groups of patients were studied: new, untreated PT (17), treated PT (12) and RT (17). Da ta consisted of: ESR, plasma fibrinogen, factor VIIIC, von Willebrand factor antigen (vWF:Ag), PDW, platelet nucleotide ratio (ATP:ADP) seru m erythropoietin (Epo), ristocetin cofactor (vWF:RiCoF), multimeric st ructure of VWF, interleukin-6, evidence of clinical ischaemia and eryt hroid colony formation. Erythroid colonies were assayed in a serum-fre e system with the addition of Epo, IL3 or alpha-IFN to produce a discr iminant function (DF) successfully used in the diagnosis of primary po lycythaemia in an earlier study. Acute phase reactants (ESR, fibrinoge n, VIIIC, vWF:Ag) and IL6 were the best discriminants, while PDW and s erum Epo were less so. ATP:ADP and clinical ischaemia were nondiscrimi natory in this study. Reduction in vWF:RiCof and in high molecular wei ght multimers were clearly associated with PT. Endogenous erythroid co lonies were nondiscriminatory, but half the PT group and only one pati ent in the RT group obtained a DF suggestive of myeloproliferative dis order. Judicious use of a battery of tests may provide support for dia gnosis of PT in difficult cases.