Pseudohyperkalemia in Serum and Plasma: The Phenomena and Its Clinical Implications

Hyperkalemia is a life threatening electrolyte derangement that must be recognized and treated quickly. Pseudohyperkalemia is defined as a difference between serum and plasma potassium concentration of more than 0.4 meq/L with serum values on the higher side when both the samples are obtained at the same time, remain at room temperature and are tested within 1 h of sample collection. Given the implication of basing medical decisions on falsely elevated potassium levels, timely identification of the entity of pseudohyperkalemia and differentiating it from true hyperkalemia becomes utmost important. Here we present a case report of a 36 year old female admitted with a provisional diagnosis of pyrexia of unknown origin with hepatosplenomegaly and anaemia under evaluation. During hospital stay her potassium levels in whole blood, serum and plasma reportedly differed significantly. An abnormal WBC count beyond assay range was reported and during subsequent investigations this lead to a peripheral smear being advised and diagnosis revealed chronic lymphoblastic leukaemia with blast crisis and 86% blast cells. In patients with leukocytosis and thrombocytosis, pseudohyperkalemia may exist in the absence of electrocardiogram changes or other clinical manifestations of true hyperkalemia thus leading to reevaluation of potassium values in serum, plasma and whole blood to arrive at the true picture.