Pseudohyperkalemia and extreme leukocytosis

Two patients with chronic lymphocytic leukemia and pseudolhyperkalemia are described. Both patients had white blood cell counts exceeding 600,000 per cubic millimeter. Routine determinations of serum potassium were elevated while normal values were obtained when plasma and serum were separated within 30 minutes of venipuncture. Incubation of clotted and heparinized specimens for 6 hours was accompanied by a marked increase of potassium levels. This study indicates that extreme leukocytosis alone can give rise to apparent hyperkalemiamtrue values can be obtained if the determinations are performed quickly after venipuncture.