Pneumatic tube transport-induced pseudohyperkalemia in patients with extreme leukocytosis: a retrospective study from a single medical center

Pseudohyperkalemia (falsely elevated serum potassium) must be distinguished from true hyperkalemia to avoid unnecessary treatment. Some case reports suggest that pneumatic tube transportation may increase the risk of pseudohyperkalemia, but comprehensive research on the topic is lacking. Here, we aimed to assess the association between WBC levels, pneumatic tube transport, and pseudohyperkalemia prevalence.

We analyzed 1188 samples collected from 240 patients between 2019 and 2022. Samples with elevated WBC counts (≥ 100 × 10³/μL) and potassium levels were included in this study. The method of specimen transportation was documented.

Pseudohyperkalemia was observed (7/390) in specimens transported using pneumatic tubes. No pseudohyperkalemia was identified with manually transported specimens (0/132). Every increase in WBC count by 100 × 10³/μL in the specimens multiplied the odds ratio of pseudohyperkalemia by 3.75 when delivered with pneumatic tube. The prevalence of pseudohyperkalemia increased as WBC count increased, especially at WBC counts greater than 200 × 10³/μL.

Pneumatic tube transport poses a risk for pseudohyperkalemia in patients with extreme leukocytosis. Physicians should anticipate odd potassium levels when interpreting blood test results. Redrawing of blood samples, manual specimen transportation, or point-of-care testing are suggested to prevent further misdiagnosis.