Pseudohyperkalémia

Pseudohyperkalemia refers to a falsely elevated serum potassium level detected in laboratory testing that does not reflect the true potassium concentration in the body. This discrepancy arises from the release of potassium from red blood cells, platelets, or white blood cells into the serum during or after blood collection and processing. It is a common pre-analytical error in laboratory diagnostics.

Several factors can contribute to pseudohyperkalemia. Traumatic venipuncture, prolonged tourniquet application, prolonged fist clenching during blood draw, or excessive agitation of the blood sample can cause red blood cells to lyse, releasing their intracellular potassium. In patients with very high platelet counts (thrombocytosis) or white blood cell counts (leukocytosis), these cells can also release potassium during clotting or prolonged incubation. Delayed sample processing or storage at room temperature for extended periods can also exacerbate cellular lysis.

The clinical significance of pseudohyperkalemia lies in its potential to lead to unnecessary and potentially harmful interventions. Accurately diagnosing true hyperkalemia is crucial as it can cause serious cardiac arrhythmias and muscle weakness. When pseudohyperkalemia is suspected, the first step is to review the patient's clinical status for signs of true hyperkalemia. If there are no such signs, repeating the potassium measurement is essential. Best practices for blood collection, such as avoiding difficult venipuncture and promptly transporting and processing the sample, are key to preventing this artifact. If the repeat serum potassium is normal, the initial elevation is attributed to pseudohyperkalemia. In some cases, a whole blood potassium measurement or a chilled sample can help differentiate between true and pseudohyperkalemia.