Pseudohyperkalemia due to Thrombocytosis: A Diagnostic and Therapeutic Case Report of an Elderly Patient

Abstract

An 87-year-old woman who was bedridden was brought in because she had been experiencing substernal pain for 10 days and right foot pain and swelling for more than a month. Laboratory tests revealed significant thrombocytosis (platelet count peaks at 2903 × 10⁹/L) and recurrent severe hyperkalemia (serum potassium up to 7.58 mmol/L). In vitro pseudohyperkalemia caused by potassium release from lysed platelets was confirmed by a significant difference between serum potassium (6.37–7.58 mmol/L) and heparinized whole-blood potassium (3.9–4.41 mmol/L). This case emphasizes how crucial it is to differentiate between artifactual hyperkalemia and significant thrombocytosis in order to prevent needless procedures.