What is the effect of preanalytical hemolysis on potassium and LDH measurements?

• A. Hemolysis falsely lowers potassium and LDH.
• B. Hemolysis has no effect on potassium or LDH measurements.
• C. Hemolysis releases intracellular potassium and LDH, falsely elevating them.
• D. Hemolysis only affects LDH, not potassium.

Answer: (C)

When red blood cells break open before analysis, their contents spill into the serum or plasma. Potassium and LDH are both highly abundant inside RBCs, so their release into the sample makes measured levels appear higher than they truly are in the patient’s circulation.

Potassium is kept at a high concentration inside red cells, while the plasma potassium normally sits around 4 to 5 mEq/L. Even a modest amount of hemolysis can significantly raise the measured potassium because the intracellular potassium from ruptured cells mixes with the plasma, leading to a falsely elevated value.

LDH is another enzyme concentrated inside red cells. When hemolysis occurs, LDH leaks out into the plasma, boosting the overall LDH activity measured in the sample. This can mimic conditions that cause tissue damage or disease, but in reality, it’s just the artifact of cellular rupture during sample handling.

Because of this, preanalytical hemolysis is a common cause of spuriously high potassium and LDH results. If a sample is hemolyzed, the results are unreliable, and repeating the draw with a non-hemolyzed sample is usually indicated.