Asymptomatic Hyponatremia and Hyperkalemia in a Patient with Leukemic Leukocytosis

A 64-year-old male presented with untreated chronic lymphocytic leukemia (leukocytes 693.2 K/mm³) and had asymptomatic persistent plasma hyponatremia and hyperkalemia (Table 1). Measured osmolality was within the reference interval (294 mOsm/kg) with low calculated osmolality (249 mOsm/kg), suggesting pseudohyponatremia due to the electrolyte exclusion effect. However, cholesterol (95 mg/dL [2.46 mmol/L]), triglycerides (217 mg/dL [1.44 mmol/L]), and plasma protein (8.2 g/dL) concentrations were unremarkable. Sodium and potassium measured by direct ion-selective electrodes in plasma from pneumatic tube-transported samples were similarly deranged, making pseudohyponatremia unlikely (Table 1).

Questions

1. What can cause pseudohyperkalemia with leukocytosis?

2. What components of sample collection and transport could affect sodium and potassium concentrations?

3. How can you evaluate if sample transport is affecting a laboratory test result?

The answers are below.

Pneumatic-tube system transport-induced pseudohyperkalemia due to cell lysis is common with leukemic leukocytosis (1–3). Pneumatic-tube system transport raised potassium (through intracellular release) and decreased sodium concentrations (through dilution by intracellular contents [intracellular (Na +) approximately 12 mmol/L, plasma (Na +) approximately 142 mmol/L]) (4). Hand-delivered specimens had sodium and potassium concentrations within the reference intervals. Calcium, chloride, and magnesium were at or slightly below the reference intervals. Water shifts equilibrate intra- and extracellular osmolality; osmolality is unaffected by leukolysis (4).

Author Contributions

The corresponding author takes full responsibility that all authors on this publication have met the following required criteria of eligibility for authorship: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; (c) final approval of the published article; and (d) agreement to be accountable for all aspects of the article thus ensuring that questions related to the accuracy or integrity of any part of the article are appropriately investigated and resolved. Nobody who qualifies for authorship has been omitted from the list.

Z. Hubler (Conceptualization-Equal, Data curation-Equal, Formal analysis-Equal, Investigation-Equal, Methodology-Equal, Visualization-Equal, Writing—original draft-Lead, Writing—review & editing-Equal), C. Farnsworth (Conceptualization-Equal, Data curation-Equal, Formal analysis-Equal, Investigation-Equal, Methodology-Equal, Project administration-Equal, Supervision-Equal, Visualization-Equal, Writing—original draft-Equal, Writing—review & editing-Equal), and N. Spies (Conceptualization-Equal, Data curation-Equal, Formal analysis-Equal, Methodology-Equal, Visualization-Equal, Writing—original draft-Equal, Writing—review & editing-Equal).

Authors’ Disclosures or Potential Conflicts of Interest

Upon manuscript submission, all authors completed the author disclosure form.

Research Funding

None declared.

Disclosures

C.W. Farnsworth has received research support from Abbott, Roche, Siemens, Sebia, Beckman Coulter, Blue Jay Diagnostics, Biomerieux, Cepheid, and Qiagen; consulting fees from Biorad, Roche, Abbott, Cytovale, and Werfen; honoraria from Abbott, Roche, and AACC, and is part of the AACC SYCL Core Committee.

References