INAPPARENT POLYCYTHEMIA-VERA - AN UNRECOGNIZED DIAGNOSIS

PURPOSE: The Polycythemia Vera Study Group (PVSG) has established usef ul criteria for the diagnosis of polycythemia vera. In some circumstan ces, an increase of plasma volume (PV) masks that of red cell mass (RC M), with hemoglobin (Hb) and hematocrit (Ht) remaining normal. This de fines the concept of inapparent polycythemia. PATIENTS AND METHODS: On e hundred and three patients seen in the hematology unit with the diag nosis of polycythemia vera were studied. There were 55 males and 48 fe males with a median age of 59 years. Ninety-five patients fulfilled th e PVSG criteria. Spontaneous erythroid colonies and low serum erythrop oietin level confirmed the diagnosis in the 8 other cases. Patients we re classified according to Hb and Ht level. RESULTS: Group A consisted of 85 patients with increased Hb and Ht defined, respectively, by Hb > 18 g/dL, Ht > 0.52 in males and Hb > 16 g/dL, Ht > 0.47 in females. Group B included 18 patients (17%) with inapparent polycythemia vera ( IPV) defined by a normal Hb and Ht value at diagnosis. In this group, the reasons to perform RCM were as follows: splenomegaly associated wi th increased platelets and/or leucocytes counts (n = 8), portal vein t hrombosis (n = 5), increased platelets or leucocytes counts without sp lenomegaly (n = 3), and isolated splenomegaly (n = 2). The two groups were balanced in terms of age, sex, leucocyte, serum iron, and platele t level. Hemoglobin and Ht levels were significantly different between the two groups. The difference between the PV was indeed highly signi ficant. The mean PV increase was + 9.5% (nL < + 20%) in group A versus + 36.3% in group B (P < 0.00005). Red cell mass was not different bet ween the two groups. CONCLUSIONS: Increased Hb or Ht should not consti tute the sole criteria for RCM determination. In the context of portal vein thrombosis, isolated hyperleucocytosis, thrombocytosis, or splen omegaly, a RCM should be performed. The frequency of IPV remains to be specified but the diagnosis of polycythemia vera is probably underest imated. (C) 1996 by Excerpta Medica, Inc.