Pseudohyperkalemia in a patient with chronic lymphoblastic leukemia and tumor lysis syndrome

Recognition of pseudohyperkalemia is essential to prevent medical mismanagement of erroneous hyperkalemia. The purpose of this case is to describe pseudohyperkalemia attributed to malignant leucocytosis in a patient with chronic lymphoblastic leukemia and tumor lysis syndrome. Methods for determination of pseudohyperkalemia are discussed.

A 75-year-old male with progressive chronic lymphoblastic leukemia was hospitalized for medical evaluation and chemotherapy administration. Notable laboratory findings included white blood cell count of 479 × 10(3) cells/µL (4.00 × 10(3) cells/µL-10.80 × 10(3) cells/µL) with 95% lymphocytes (20%-50%) and 5% blasts (zero) present in the differential, serum potassium 9.8 mM/L (3.4 mM/L-5.0 mM/L), uric acid of 11.8 mg/dL (3.5 mg/dL-8.0 mg/dL), serum creatinine 1.47 mg/dL (0.60 mg/dL-1.30 mg/dL), and lactate dehydrogenase of 2529 IU/L (100 IU/L-220 IU/L). The patient was anemic (Hb 7.6 g/dL (14.0 g/dL-18.0 g/dL)) and thrombocytopenic (17 × 10(3) platelets/μL (140 × 10(3) platelets/μL-400 × 10(3) platelets/μL)). There were no electrocardiographic findings indicating systemic hyperkalemia. Repeat analysis of the blood potassium level using a heparinized tube assayed immediately after specimen collection demonstrated a plasma potassium level 4.1 mM/L. Subsequent analysis of specimens using similar methodology demonstrated potassium results within the normal limits despite continued laboratory evidence of pseudohyperkalemia. Based on the patient's conscious and interactive condition, ECG findings, and normal plasma potassium level following immediate analysis, the diagnosis of pseudohyperkalemia was made. Laboratory findings of pseudohyperkalemia persisted throughout the period of leukocytosis.

This case describes pseudohyperkalemia attributed to malignant leucocytosis in a patient with chronic lymphoblastic leukemia (CLL). Practitioners should consider pseudohyperkalemia as the underlying cause of elevated potassium levels in patients with malignant leucocytosis who do not have signs or symptoms of systemic hyperkalemia.