Blood p50 evaluation enhances diagnostic definition of isolated erythrocytosis

J Intern Med. 2009 Feb;265(2):266-74. doi: 10.1111/j.1365-2796.2008.02014.x. Epub 2008 Sep 10.


Background: High oxygen-affinity haemoglobin variants and 2,3-diphosphoglycerate (2,3-DPG) deficiency are inherited diseases generating low tissue oxygen tension and erythropoietin-driven erythrocytosis, that characterizes the clinical phenotype of patients. Level of blood p50 (the oxygen tension at which haemoglobin is 50% saturated) is used to recognize these conditions.

Objectives: To define the clinical utility of blood p50 measurement in the diagnosis of isolated erythrocytosis.

Subjects and design: Venous blood p50 measurement was included in the diagnostic work-up of 102 consecutive patients with isolated erythrocytosis besides blood cell count, arterial oxygen saturation, serum erythropoietin measurement and screening for JAK2 mutations.

Setting: Haematological Outpatient Section at University Hospital.

Results: Seven patients had relative erythrocytosis. Among 95 patients with absolute erythrocytosis, 4 (4.2%) had decreased p50 level. The extended study of family members revealed a familial inheritance. Two families had haemoglobin variants already described as Haemoglobin Malmö and Haemoglobin San Diego. In one family, the proband had a new high oxygen-affinity haemoglobin variant (Haemoglobin Safi) resulting from the transversion C-->A at codon 81 of the alpha2-globin gene. In the last family, a deficiency of 2,3-DPG was found. Within the 91 patients with normal p50 values, 46 (51%) had secondary erythrocytosis, 13 (14%) polycythemia vera and 32 (35%) idiopathic erythrocytosis.

Conclusions: This study suggests that the investigation of blood p50 level may be useful to define diagnosis in patients with isolated erythrocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Algorithms
  • Biomarkers / blood
  • Blood Cell Count
  • Blood Gas Analysis
  • Erythropoietin / blood*
  • Female
  • Hemoglobins, Abnormal / genetics
  • Humans
  • Janus Kinase 2 / blood
  • Janus Kinase 2 / genetics
  • Male
  • Middle Aged
  • Oxygen / blood*
  • Polycythemia / blood*
  • Polycythemia / diagnosis
  • Young Adult


  • Biomarkers
  • Hemoglobins, Abnormal
  • Erythropoietin
  • Janus Kinase 2
  • Oxygen