title: Early recognition of reverse pseudohyperkalemia in heparin plasma samples during leukemic hyperleukocytosis can prevent iatrogenic hypokalemia.
abstract: OBJECTIVE
  To investigate the cause of apparent hyperkalemia in leukemic heparin plasma.
  
  
  METHODS
  Lithium heparin plasma and serum samples from a patient with chronic lymphocytic leukemia (CLL) with hyperleukocytosis were transported by either a pneumatic tube system or manual transport and analyzed either immediately or after 4 h.
  
  
  RESULTS
  Pneumatic tube transported samples resulted in higher plasma potassium levels than manually transported samples. Serum potassium was lower than plasma potassium, confirming the suspicion of "reverse" pseudohyperkalemia. Letting the pneumatic tube transported samples stand on the bench for 4 h before centrifugation surprisingly resulted in decreased or unchanged plasma potassium.
  
  
  CONCLUSIONS
  The reverse pseudohyperkalemia in heparin plasma samples from a CLL patient was caused by pneumatic tube transport. Our results suggest extracellular leakage of potassium, followed by active transport of potassium into intact leukemic cells. This is the first Swedish case of reverse pseudohyperkalemia in a CLL patient, where clinical suspicion of false hyperkalemia and awareness of the phenomenon lead to a rapid laboratory diagnosis. The demonstration of reverse pseudohyperkalemia prevented potentially dangerous medical interventions, such as potassium lowering treatment.
authors.affiliation: Division of Clinical Chemistry and Blood Coagulation, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden. Daniel.Garwicz@medsci.uu.se
authors.forename: Daniel
authors.initials: D
authors.lastname: Garwicz
authors.forename: Mattias
authors.initials: M
authors.lastname: Karlman
mesh_terms: D000368:Aged; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D006947:Hyperkalemia / Q000097:blood* / Q000517:prevention & control*; D007049:Iatrogenic Disease / Q000517:prevention & control*; D007938:Leukemia / Q000097:blood*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000097:blood; D007958:Leukocyte Count; D007964:Leukocytosis / Q000097:blood*; D008297:Male; D010949:Plasma / Q000378:metabolism*; D011188:Potassium / Q000097:blood
chemical_list: D006493:Heparin; D011188:Potassium