Differences between true hyperkalemia and pseudo hyperkalemia?
Pseudohyperkalemia is suspected when the laboratory value of the measured potassium is high but the patient does not manifest signs of hyperkalemia such as an abnormal EKG.
Few researchers have defined pseudohyperkalemia as a difference between serum and plasma potassium concentrations of more than 0.4 mmol/L when samples remain at room temperature and are tested within one hour of collection.
Pseudohyperkalemia due to mechanical cell lysis can be identified by keeping the tourniquet time less than 1 minute and avoiding fist clenching to obtain an atraumatic sample. Serum is the supernatant obtained by centrifuging a blood sample that has been allowed to clot after collection in a red top tube (no anticoagulant). Plasma is the supernatant obtained after removing cells by centrifuging a sample of blood collected in tube with an anticoagulant (lavender top or light blue top). The process of clotting causes cell lysis and thus release of intracellular potassium. In pseudohyperkalemia, the plasma potassium will be normal in the face of an elevated serum potassium.
