Pseudohyperkalemia in a Patient with Leukemia: A Diagnostic Pitfall in Emergency Medicine

Pseudohyperkalemia is characterized by a falsely elevated serum potassium concentration, often due to cellular disruption during blood sample collection, processing, or transport. Accurate differentiation between pseudohyperkalemia and true hyperkalemia is vital to prevent inappropriate treatment, which can lead to iatrogenic hypokalemia.

We present a case of a 67-year-old woman with hypertension and T-cell prolymphocytic leukemia who presented to the emergency department with fever and hypotension. Initial laboratory results indicated hyperkalemia, acute kidney injury, metabolic acidosis, and extreme leukocytosis. Despite aggressive management for hyperkalemia, persistent elevation of potassium levels without electrocardiographic changes raised suspicion for pseudohyperkalemia. Subsequent investigations, including the use of different blood collection tubes, revealed disparate potassium concentrations, confirming pseudohyperkalemia due to potassium leakage from fragile leukemia cells. The patient's potassium levels normalized upon using clot-activator tubes, and she was discharged without complications. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case underscores the importance of recognizing pseudohyperkalemia, especially in patients with leukocytosis and incompatible clinical manifestations. Proper blood-sample collection and handling, along with awareness of confounding factors, are essential to prevent misinterpretation of laboratory results and avoid unnecessary treatments. In clinical settings, heparin tubes, while convenient, may contribute to pseudohyperkalemia in patients with fragile blood cells, such as those with leukemia, due to mechanical stress during sample processing. Early recognition and appropriate diagnostic approaches are crucial to ensure accurate patient management and avoid potential harm from unwarranted interventions.