Spurious hyperkalemia, also known as pseudohyperkalemia, is a situation where a falsely elevated serum potassium level is measured in a patient, even though their true potassium level is normal. This can occur in the context of leukocytosis, where an elevated white blood cell count can cause potassium to be released from cells during blood sample collection or processing.
Causes of Spurious Hyperkalemia in Leukocytosis:
Mechanical trauma during blood collection:
Using vacuum tubes, pneumatic tubes for transport, or improper phlebotomy techniques can cause cell lysis and release of potassium.
Sample handling:
Prolonged storage, vigorous shaking, or improper centrifugation can also lead to cell lysis and release of potassium.
Leukemic cell fragility:
Leukemic cells, particularly in conditions like chronic lymphocytic leukemia (CLL), are more fragile and susceptible to lysis.
Specific laboratory methods:
Using serum samples for potassium measurement instead of plasma or whole blood can also contribute to spurious results, as potassium is more likely to be released from cells during clot formation in serum.
Diagnosis and Management:
Confirmatory testing:
To differentiate between true hyperkalemia and pseudohyperkalemia, it’s crucial to measure potassium in whole blood or plasma samples obtained with heparinized syringes and analyzed quickly, ideally at the point of care or with an arterial blood gas analyzer.
Clinical context:
In the absence of clinical signs and symptoms of hyperkalemia, renal dysfunction, or medications that can elevate potassium, a high index of suspicion for pseudohyperkalemia should be maintained, particularly in patients with leukocytosis.
Avoidance of unnecessary treatment:
Treating pseudohyperkalemia can lead to dangerous iatrogenic hypokalemia (low potassium). Instead, it’s essential to identify and correct the underlying cause of the false elevation, such as improving sample collection and handling techniques.
Importance of Recognizing Pseudohyperkalemia:
Preventing iatrogenic hypokalemia:
Incorrect treatment of pseudohyperkalemia can lead to life-threatening hypokalemia.
Avoiding unnecessary investigations:
Identifying pseudohyperkalemia allows for a more targeted approach to investigation and treatment.
Improving patient care:
Accurate diagnosis and management of pseudohyperkalemia, especially in patients with leukocytosis, contribute to better patient outcomes.