It has been reported many times that falsely elevated potassium can be seen in patients with severe leukocytosis from chronic lymphocytic leukemia (CLL). Early recognition of factitious hyperkalemia is very important to prevent inappropriate and potentially hazardous treatment. One case we observed in our institution, again, emphasized the importance and urgency to recognize these instances.
In this case, patient was a 58 year old male with recently diagnosed CLL. His potassium level rose from normal levels at admission to 8.9 mmol/L on repeated blood draws. Patient was asymptomatic with good strength on physical exam, and had no abnormalities on EKG or telemetry. Insulin/glucose and calcium gluconate was administered to correct potassium level and to prevent cardiac effect of hyperkalemia. The hyperkalemia result was initially thought to be due to emerging tumor lysis syndrome and was not brought to our attention until another specimen obtained had a potassium level greater than the measurable range (10.0 mmol/L). Specimens were not hemolyzed and white blood cell count was as high as 455K/µL.
Given his history of CLL, we suspected pseudohyperkalemia, an entity that has been attributed to the combination of the fragility of the leukemic lymphocytes and the mechanical stress on the cells during specimen transportation and centrifugation. Our clinical team was notified immediately, and a whole blood specimen was collected and hand carried to the laboratory. Without centrifuging, the whole blood specimen was analyzed on a blood gas analyzer and showed a potassium level of 4.2 mmol/L!!! Potassium-lowering treatment was discontinued.
Artifactually elevated potassium level is commonly seen due to red blood cell hemolysis, but not well appreciated is its occasional occurrence in patients with extreme leukocytosis from CLL. It is important for laboratorians to recognize this pattern and to notify our clinical teams so that patients are not inappropriately treated.
-Xin Yi, PhD, DABCC, FACB, is a board-certified clinical chemist, currently serving as the Co-director of Clinical Chemistry at Houston Methodist Hospital in Houston, TX and an Assistant Professor of Clinical Pathology and Laboratory Medicine at Weill Cornell Medical College.