Which condition is most likely to produce a falsely elevated serum phosphate due to a hemolyzed specimen?

Which condition is most likely to produce a falsely elevated serum phosphate due to a hemolyzed specimen?

• A. Fasting prior to draw
• B. Hemolyzed sample
• C. Prolonged tourniquet time without failure
• D. Recent exercise

Answer: (B)

A hemolyzed specimen causes a falsely elevated serum phosphate because red blood cells contain a much higher concentration of phosphate than plasma. When cells rupture, their intracellular phosphate is released into the serum, raising the measured level independent of the patient’s true phosphate status. The more hemolysis, the greater the apparent increase. Other scenarios like fasting, brief or prolonged tourniquet time, or recent exercise can affect phosphate through different pathways, but they don’t produce the specific spike caused by release of intracellular phosphate from lysed red cells.

A hemolyzed specimen causes a falsely elevated serum phosphate because red blood cells contain a much higher concentration of phosphate than plasma. When cells rupture, their intracellular phosphate is released into the serum, raising the measured level independent of the patient’s true phosphate status. The more hemolysis, the greater the apparent increase. Other scenarios like fasting, brief or prolonged tourniquet time, or recent exercise can affect phosphate through different pathways, but they don’t produce the specific spike caused by release of intracellular phosphate from lysed red cells.