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Mary M Barrett, Y Victoria Zhang, Normal Potassium in the Presence of Gross Hemolysis, Clinical Chemistry, Volume 61, Issue 8, 1 August 2015, Pages 1114–1115, https://doi.org/10.1373/clinchem.2015.238899
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Case Description
A 15-year-old boy presented to the emergency department with acute development of fever and chills. Physical exam revealed a blood pressure of 86/61, jaundice with scleral icterus, and dark urine. Laboratory tests (increased free hemoglobin, increased lactate dehydrogenase, and decreased haptoglobin) revealed a direct antiglobulin test (DAT)-negative hemolytic anemia. Sequential serum potassium measurements remained normal to low (reference interval, 3.6–5.2 mmol/L) through the majority of his disease course (Fig. 1).
Potassium concentrations over the course of the hospital stay.
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Questions for Discussion
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The answers are on the next page.
Answers
Hemolysis releases intracellular potassium. For hemolysis occurring after the sample is drawn, the serum potassium would appear artificially high (1, 2). However, when hemolysis occurs in vivo (e.g., a hemolytic anemia), the patient's potassium-regulating systems will quickly normalize the serum potassium to prevent hyperkalemia (3). Some possible causes of DAT-negative hemolysis include thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, disseminated intravascular coagulation, infection (e.g., malaria), drug- or toxin-induced hemolysis, hypersplenism, and Wilson disease (4).
