Endocrine Abstracts

Introduction: Pseudohyperkalaemia is defined as a raised serum potassium with concurrent plasma potassium levels within the normal range. There is usually a slight difference between serum and plasma potassium levels, owing to release of potassium from activated platelets during clotting; pseudohyperkalaemia occurs where there is a difference greater than 0.4mmol/L between the two values, in the absence of symptoms or ECG changes. While pseudohyperkalaemia occurs relatively frequently in primary care, owing to difficulties in storage and transportation of samples, it is far less common in the hospital setting.

Case: A gentleman with a background of ulcerative colitis, pancreatic cancer and diabetes mellitus was seen during a routine consultation while an inpatient for management of his diabetes. Routine blood tests showed a serum potassium of 6.0 mmol/l. There were no concerning ECG features; the hyperkalaemia was refractory to standard treatment. He did not take any medications that would predispose him to hyperkalaemia, and was adherent to a low-potassium diet as advised by a dietitian. Random cortisol was checked and was found to be 464 nmol/l, excluding Addison’s disease. It was noted that he had significant thrombocytosis, with an apparent positive correlation between his platelet count and serum potassium levels. Repeat blood tests showed serum potassium of 5.6 mmol/l; the same sample was simultaneously run through a blood gas analyser, with a potassium of 4.8 mmol/l. Given all other causes of hyperkalaemia had been excluded, it would appear that this was a case of pseudohyperkalaemia secondary to thrombocytosis. He has since been referred onto a Haematologist for further investigation.

Conclusion: Pseudohyperkalaemia should always be considered in patients with unexplained, hyperkalaemia where the clinical context or progress is unusual. Identifying pseudohyperkalaemia may avoid subjecting patients to unnecessary investigations and potentially harmful treatments.