An 85-year-old female with a ten-year history of high-risk progressive chronic lymphocytic leukemia (CLL) presented to the Emergency Department with vertigo and headache. Upon initial evaluation, her laboratory results showed a white blood cell (WBC) count of 233 x 109 cells/L (reference interval: 3.5–10.5 x 109 cells/L), platelet count of 136 x 109 platelets/L (reference interval: 150–450 x 109 platelets/L), and plasma potassium of 6.6 mmol/L (reference interval: 3.6–5.2 mmol/L). No conduction abnormalities were seen on her EKG. Repeat measurement of potassium by point-of-care testing (POCT) was 3.9 mmol/L. Additional serum and plasma samples were sent to the core laboratory for analysis and potassium results were 3.5, and 6.1 mmol/L, respectively.
Brooke Katzman, Ph.D.
Fellow, Clinical Chemistry
Nikola Baumann, Ph.D.
Consultant, Division of Clinical Core Laboratory Services
Assistant Professor of Laboratory Medicine and Pathology,
Mayo Clinic College of Medicine