How is pseudohyperkalemia (elevated potassium levels due to laboratory error) diagnosed and managed?

Diagnosis and Management of Pseudohyperkalemia

Pseudohyperkalemia should be ruled out before initiating treatment for hyperkalemia by obtaining a plasma potassium measurement and comparing it to serum potassium, with a difference >0.4 mEq/L confirming pseudohyperkalemia. 1

Definition and Diagnosis

• Pseudohyperkalemia is defined as an artificial rise in serum potassium with normal effective plasma potassium concentration (difference >0.4 mEq/L between serum and plasma values) 1
• To diagnose pseudohyperkalemia, compare potassium levels in both serum and plasma samples collected simultaneously and processed within 1 hour 1
• Absence of clinical symptoms and ECG changes of hyperkalemia despite elevated potassium levels strongly suggests pseudohyperkalemia 2

Common Causes of Pseudohyperkalemia

• Poor phlebotomy techniques including:
  • Excessive fist clenching during blood collection 3
  • Prolonged tourniquet application 4
  • Hemolysis during sample collection or processing 3
• Sample processing issues:
  • Delayed specimen processing 3
  • Inappropriate sample storage conditions 5
  • Contamination during collection or analysis 4
• Patient-related factors:
  • Extreme leukocytosis or thrombocytosis 1, 6
  • Familial pseudohyperkalemia (genetic condition causing excessive K+ leak from erythrocytes) 5, 4

Diagnostic Algorithm

1. When hyperkalemia is detected:

   • Check for clinical symptoms (muscle weakness, paresthesias) 3
   • Obtain ECG to look for hyperkalemia changes (peaked T waves, flattened P waves, prolonged PR interval, widened QRS) 7
   • If asymptomatic with normal ECG, suspect pseudohyperkalemia 2

2. Confirm pseudohyperkalemia by:

   • Collecting both serum and plasma samples simultaneously 1
   • Processing samples promptly (within 1 hour) 1
   • Comparing potassium values (difference >0.4 mEq/L confirms pseudohyperkalemia) 1
   • Checking complete blood count for leukocytosis or thrombocytosis 1, 6

3. If pseudohyperkalemia is confirmed:

   • Document in patient's chart to prevent unnecessary treatment 2
   • Consider special handling of future blood samples 4

Management Approach

• For confirmed pseudohyperkalemia:

  • No specific treatment is required as the elevated potassium is an in vitro phenomenon 5, 2
  • Avoid unnecessary and potentially harmful hyperkalemia treatments 2

• For future blood draws in patients with known pseudohyperkalemia:

  • Use proper phlebotomy techniques (minimal tourniquet time, avoid excessive fist clenching) 3, 4
  • Process samples immediately 3
  • Consider using plasma rather than serum for potassium measurement 1, 6
  • In cases of extreme leukocytosis or thrombocytosis, consider point-of-care testing or whole blood potassium measurement 1

Special Considerations

• Reverse pseudohyperkalemia may occur in some leukemic patients where plasma potassium exceeds serum potassium due to heparin-induced cell membrane damage 6
• Familial pseudohyperkalemia should be considered when there are discrepant potassium values between different healthcare settings 5
• The European Society of Cardiology warns against failing to rule out pseudohyperkalemia before initiating treatment for hyperkalemia 7

Common Pitfalls

• Treating pseudohyperkalemia as true hyperkalemia can lead to iatrogenic hypokalemia and associated complications 2
• Failing to recognize pseudohyperkalemia in patients with hematologic disorders (leukemia, thrombocytosis) 1, 6
• Overlooking the impact of sample collection and processing techniques on potassium values 3, 4