Endocrine Abstracts

Introduction: Pseudohyperkalaemia is one of the most common testing errors that occur in clinical practice. It’s commonly due to pre-analytical factors many of which are clinically well recognised. These include incorrect sampling, delay in sample processing and haemolysis to name a few. However non-recognition of some rarer causes like thrombocytosis often results in initial inappropriate, potentially dangerous treatment. Here we present one such case of pseudohyperkalaemia in a patient with myeloproliferative disorder in the context of acute kidney injury.

Case: A 70-year-old gentleman was admitted to hospital with abdominal pain and vomiting. This was later diagnosed to be due to cholecystitis. He was also found to have severe hyperkalaemia of 7 mmol/l, acute kidney injury with an eGFR 48 (68 about a month ago), Hb: 106 g/l, Platelets: 1,035 109/l, WCC: 54.6 10⁹/l and Neutrophils: 52 109/l. Although his point of care (POC) venous blood gas potassium was 5.4 and ECG was normal, he was treated with intravenous insulin dextrose infusion due to two lab K levels being ≥7 mmol/l. He was not on any medications that could raise potassium. He had a past medical history of JAK2+ve myeloproliferative disorder, hypertension, gout, and glaucoma. It was then noted that his hydoxycarbamide was stopped about a month ago, before his hip fracture surgery, but was not restarted due to oversight. This was promptly restarted and a possibility of pseudohyperkalaemia was considered. A repeat serum and plasma K with Lithium heparin tube were sent and the results were 6.7 and 5.5 mmol/l respectively confirming pseudohyperkalaemia due to thrombocytosis. Subsequently, POC potassium was used to make clinical decision. His K came down to 3.8 mmol/l along with platelet count of 404 10⁹/l and normal WBC, on day 5 of restarting hydroxycarbamide.

Discussion and conclusion: Hyperkalaemia is a potentially fatal condition and should be managed promptly. However, pseudohyperkalaemia must be excluded particularly when there is evidence of thrombocytosis as it could lead to inappropriate corrective treatment that may cause hypokalaemia an equally dangerous condition. Pseudohyperkalaemia in the context of thrombocytosis is due to in vitro release of potassium from activated platelets during the process of clotting in serum tubes. Literature suggests considering pseudohyperkalaemia when platelet count is more than 500 + 10⁹/l, and measuring plasma K using heparinised tube or whole blood K with POC venous blood gas analyser for making appropriate diagnosis and to avoid unnecessary and potentially harmful treatment.