Importantly, rupture of leukocytes and increased clotting cannot be detected by spectrophotometric measurements of hemolysis. Additionally, post-splenectomy reactive thrombocytosis has been reported to cause pseudohyperkalemia in numerous case studies (8–11). Patients with essential thrombocythemia, polycythemia vera, and myelofibrosis were most at risk for pseudohyperkalemia (7). High risk for thrombocytosis-related pseudohyperkalemia has been identified for samples with platelet counts above 400-500 K/cu mm (3,5,6). In samples from patients with thrombocytosis, the increased clotting causes increased release of potassium from platelets, falsely elevating serum potassium results. Patients with chronic lymphoid leukemia (CLL), T-cell acute lymphoblastic leukemia (T-ALL), and mantle cell lymphoma are most at risk for pseudohyperkalemia in serum samples due to the fragility of abnormal white cells (3,5). High risk for leukocytosis-related pseudohyperkalemia has been identified in samples with a white blood cell (WBC) count of 50-100 K/cu mm or greater (3,4). In samples from patients with leukocytosis, the force experienced during centrifugation can cause the excess white blood cells to lyse, releasing potassium and falsely elevating serum potassium results. When significant leukocytosis, thrombocytosis, hyperproteinemia, or hyperlipidemia are present, whole blood potassium is recommended over serum potassium. The American Society of Clinical Pathology suggests a hemolysis goal of 2%, however, variable collection practices often lead to much higher hemolysis rates (1,2). Certain collection techniques increase hemolysis, such as collection through an IV line, use of small gauge needles, and collection using a syringe. The Data: In vitro hemolysis is prevalent throughout both inpatient and outpatient settings. Due to the inability to measure hemolysis in whole blood testing, serum potassium measurements are recommended in most situations. Therefore, whole blood potassium measurements may be at risk of false elevations due to unrecognized in vitro hemolysis. Instruments that measure whole blood potassium do not have the functionality for spectrophotometric hemolysis measurement. When hemolysis is measured above the laboratory’s established threshold, the corresponding serum result is not reported. For potassium, which is released from erythrocytes upon cell rupture, even low levels of hemolysis can significantly increase serum potassium measurements. Serum testing in the centralized laboratory uses a spectrophotometric measurement of serum hemoglobin to estimate hemolysis and thus ensure the reliability of reported results. For potassium, the largest concern is rupture of erythrocytes leading to release of potassium. Like all lab tests biological, pre-analytical, and analytical variation can affect the final result. when significant thrombocytosis, leukocytosis, hyperproteinemia, or hyperlipidemia are presentĬontext: Medical decision making is contingent upon reliability of lab testing.for immediate management, such as during codes or surgeries.Whole blood potassium should be ordered in the following scenarios: Serum potassium measurements are recommended for most clinical situations. During analysis of whole blood, instruments do not have the functionality for spectrophotometric hemolysis measurement. Q: Should I always order a whole blood when there is concern for hemolysis?

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