Pseudohyperkalemia vs Reverse Hyperkalemia



Pseudohyperkalemia and reverse pseudohyperkalemia are both conditions where potassium levels appear falsely elevated.



Pseudohyperkalemia:

This condition is typically identified when serum potassium levels are elevated, but plasma potassium levels remain normal.

Mechanism:

 • Potassium leaks from cells (usually platelets, leukocytes, or red blood cells) into the serum during clotting or sample processing.

 • Occurs after blood is drawn, not in the patient.

Causes:

 • Thrombocytosis (high platelet count): When serum is used (which includes clotting), platelets release potassium during clotting.

 • Leukocytosis (especially extreme, e.g., >100,000/mm³ in leukemia): Fragile or overabundant white cells may rupture during handling.

 • Hemolysis during phlebotomy or processing.

 • Prolonged tourniquet time, fist clenching, or rough venipuncture.

Key Clues:

 • Serum potassium is high.

 • Plasma potassium (collected in heparinized tube, no clotting) is normal.

 • No clinical signs of hyperkalemia.



Reverse Pseudohyperkalemia:

A rarer condition where plasma potassium is falsely elevated, but serum potassium is normal.

Mechanism:

 • In certain leukemias (especially chronic lymphocytic leukemia), fragile leukemic white cells lyse in heparinized (plasma) tubes, releasing potassium.

 • In serum tubes, clotting traps and removes these cells before lysis occurs, so potassium stays normal.

Causes:

 • Seen mainly in leukemic patients with very high WBC counts and fragile cells.

 • Often associated with CLL (chronic lymphocytic leukemia).

Key Clue:

 • Plasma potassium high.

 • Serum potassium normal or lower.

 • No symptoms of hyperkalemia.



Always correlate potassium levels with:

 • Hemolysis index (check sample quality)

 • Platelet/WBC count

 • Serum vs plasma potassium

 • ECG findings — if no changes in ECG despite high K+, consider pseudohyperkalemia.



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