Pseudohyperkalemia due to pneumatic tube transport in a leukemic patient.

Pseudohyperkalemia is an elevation in measured serum or plasma potassium levels caused by mechanical release of potassium from cells during phlebotomy or specimen processing. We describe a case of pseudohyperkalemia caused by mechanical disruption of white blood cells from a leukemic patient because of pneumatic tube transport of the specimen. This is the first description of pneumatic tube transport causing pseudohyperkalemia, and clinicians should be aware of this potential cause of false elevation of plasma potassium levels.