title: Inapparent polycythemia vera: an unrecognized diagnosis.
abstract: OBJECTIVE
  The Polycythemia Vera Study Group (PVSG) has established useful criteria for the diagnosis of polycythemia vera. In some circumstances, an increase of plasma volume (PV) masks that of red cell mass (RCM), with hemoglobin (Hb) and hematocrit (Ht) remaining normal. This defines the concept of inapparent polycythemia.
  
  
  METHODS
  One hundred and three patients seen in the hematology unit with the diagnosis of polycythemia vera were studied. There were 55 males and 48 females with a median age of 59 years. Ninety-five patients fulfilled the PVSG criteria. Spontaneous erythroid colonies and low serum erythropoietin level confirmed the diagnosis in the 8 other cases. Patients were 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 with increased platelets and/or leucocytes counts (n = 8), portal vein thrombosis (n = 5), increased platelets or leucocytes counts without splenomegaly (n = 3), and isolated splenomegaly (n = 2). The two groups were balanced in terms of age, sex, leucocyte, serum iron, and platelet level. Hemoglobin and Ht levels were significantly different between the two groups. The difference between the PV was indeed highly significant. 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 between the two groups.
  
  
  CONCLUSIONS
  Increased Hb or Ht should constitute the sole criteria for RCM determination. In the context of portal vein thrombosis, isolated hyperleucocytosis, thrombocytosis, or splenomegaly, a RCM should be performed. The frequency of IPV remains to be specified but the diagnosis of polycythemia vera is probably underestimated.
authors.affiliation: Department of Hematology, Hôpital Pontchaillou, Rennes, France.
authors.forename: T
authors.initials: T
authors.lastname: Lamy
authors.forename: A
authors.initials: A
authors.lastname: Devillers
authors.forename: M
authors.initials: M
authors.lastname: Bernard
authors.forename: A
authors.initials: A
authors.lastname: Moisan
authors.forename: I
authors.initials: I
authors.lastname: Grulois
authors.forename: B
authors.initials: B
authors.lastname: Drenou
authors.forename: L
authors.initials: L
authors.lastname: Amiot
authors.forename: R
authors.initials: R
authors.lastname: Fauchet
authors.forename: P Y
authors.initials: PY
authors.lastname: Le Prise
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D004906:Erythrocyte Count; D005260:Female; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D011087:Polycythemia Vera / Q000175:diagnosis*
chemical_list: D006454:Hemoglobins