What are the causes of pseudo‑hyperkalaemia?

Causes of Pseudo-Hyperkalemia

Pseudo-hyperkalemia is caused by release of potassium from blood cells or tissue during or after blood sampling, resulting in falsely elevated potassium levels in the test tube without true hyperkalemia in the body. 1

Primary Mechanisms of Pseudo-Hyperkalemia

The key distinction is that pseudo-hyperkalemia represents an in vitro phenomenon—the elevated potassium exists only in the blood sample, not in the patient's circulation. This occurs through several specific mechanisms:

Blood Cell-Related Causes

• Hemolysis (most common): Rupture of red blood cells during collection or processing releases intracellular potassium into serum 1, 2

  • Can occur in the test tube (artifact) or in the body (true hyperkalemia)
  • Clinicians must determine which scenario applies 1

• Thrombocytosis: Excessive platelet counts lead to potassium release during clotting 3, 4, 5

  • Particularly relevant in cancer patients with reactive thrombocytosis 3
  • Documented in patients with atopic dermatitis and elevated platelet counts 4

• Leukocytosis: Fragile white blood cells in leukemia release potassium during sample processing 6, 5

  • Especially problematic in T-cell prolymphocytic leukemia and polycythemia vera 6, 5

Collection and Handling Errors

• Prolonged tourniquet application with fist clenching: Causes potassium release from muscle cells during venipuncture 2, 5

• Temperature-dependent storage:

  • Storing samples at low temperatures (4°C or 20°C) for 4-8 hours causes significant potassium elevation 7, 8
  • Particularly problematic during cold seasons when samples may be refrigerated 7
  • Can increase potassium by 5% at 4 hours and 20% at 8 hours 8

• Contamination from IV lines: Drawing blood from intravenous access through which potassium was administered 5

• EDTA contamination: Rare but documented cause 5

Familial Pseudohyperkalemia (FP)

• Genetic disorder (ABCB6 gene variant, autosomal dominant) causing temperature-dependent potassium efflux from red blood cells at sub-physiological temperatures 7, 9
• Manifests as seasonal variation in potassium levels, with apparent hyperkalemia during colder months 7
• Potassium elevation occurs only when samples stored below body temperature 7, 9

Diagnostic Approach

When pseudo-hyperkalemia is suspected, repeat measurement with appropriately sampled blood or obtain an arterial sample 1. Key diagnostic steps include:

1. Check for hemolysis indicators in the laboratory report
2. Review complete blood count for thrombocytosis (>450,000/μL) or leukocytosis
3. Assess clinical context: Absence of ECG changes despite severe hyperkalemia strongly suggests pseudo-hyperkalemia 6, 9
4. Compare serum vs. plasma potassium: Plasma typically 0.1-0.4 mEq/L lower than serum due to platelet potassium release during clotting 2
5. Use different collection tubes: Heparin tubes may contribute to pseudo-hyperkalemia in patients with fragile cells; clot-activator tubes may provide more accurate results 6
6. Test storage conditions: If seasonal pattern observed, replicate testing at different temperatures (37°C vs. 20°C vs. 4°C) 7

Critical Clinical Pitfalls

The most dangerous error is treating pseudo-hyperkalemia as true hyperkalemia, which can cause iatrogenic hypokalemia—itself life-threatening 3, 6, 9. Always verify hyperkalemia before initiating aggressive treatment, especially when:

• Potassium >6.5 mEq/L without ECG changes
• Patient asymptomatic despite severe laboratory values
• Thrombocytosis or leukocytosis present
• Seasonal pattern of elevated potassium noted
• Repeat testing shows spontaneous normalization without intervention

Recognition of pseudo-hyperkalemia prevents unnecessary emergency department visits, inappropriate treatments (insulin-glucose, calcium, dialysis), and potential harm from induced hypokalemia 3, 6, 5.