title: Pseudohyperkalemia in patients with increased cellular components of blood.
abstract: OBJECTIVE
  We performed a study to investigate the difference between serum and plasma potassium concentration in patients with increase in one or more of the cellular components of blood.
  
  
  METHODS
  This study was performed in two phases. During the first phase, we performed a cross-sectional comparison of the difference between serum and plasma potassium concentration (Dk) in 341 patients with the various clinical conditions where pseudohyperkalemia has been described, as well as with secondary or spurious erythrocytosis and in 30 normal controls. A cut-off value of Dk discriminating polycythemia vera from other erythrocytoses was estimated. In the second phase we studied the significance of this cut-off value as predictor of polycythemia vera in 90 naive patients who were referred with an elevated hematocrit.
  
  
  RESULTS
  Dk was significantly increased in the groups with platelet, erythrocyte or with a mixed type disorder compared to the controls (P < 0.01). Among these groups, Dk was significantly increased in the groups with thrombocytosis and mixed type disorder, compared to the group with erythrocytosis (both P < 0.01). A cut-off value of Dk discriminating polycythemia vera from other erythrocytoses was estimated (0.70 mmol/L). Dk (> or = 0.70 mmol/L), platelet and white blood cell count were identified as significant independent predictors of polycythemia vera.
  
  
  CONCLUSIONS
  The Dk is increased in patients with erythrocytoses, thrombocytoses or both. This phenomenon is more profound in patients with a mixed type disorder, such as polycythemia vera patients, compared to those with erythrocytoses alone.
authors.affiliation: Second Department of Internal Medicine, National University of Athens Medical School, First Regional Transfusion Center, Hippokration General Hospital, Athens, Greece. nsevast@med.uoa.gr
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Sevastos
authors.forename: George
authors.initials: G
authors.lastname: Theodossiades
authors.forename: Savvas P
authors.initials: SP
authors.lastname: Savvas
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Tsilidis
authors.forename: Stamatis
authors.initials: S
authors.lastname: Efstathiou
authors.forename: Athanasios J
authors.initials: AJ
authors.lastname: Archimandritis
mesh_terms: D001772:Blood Cell Count; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D006801:Humans; D006947:Hyperkalemia / Q000097:blood*; D011188:Potassium / Q000097:blood
chemical_list: D011188:Potassium