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August 2023 Quick Question: Hemolysis

Our August 2023 Quick Question was a poll that attracted 26 responses. The question was “How do you distinguish ex vivo from intravascular plasma hemolysis?”

  1. Redraw specimen: 11 [42%]
  2. Analyze plasma LDH: 0
  3. Analyze plasma potassium: 4 [15%]
  4. Analyze plasma hemoglobin: 4 [15%]
  5. Analyze plasma haptoglobin: 7 [28%]

For decades, we’ve redrawn specimens when plasma hemolysis is visible. Inpatients dislike additional venipunctures, and outpatients must be called back. Hemolysis interferes with absorbance and implies ex vivo platelet and possibly procoagulant activation. Many automated coagulometers offer a plasma hemolysis quantitation channel that enables the chosen assay to proceed if the level of hemolysis has been found to offer no interference.

The key issue that our poll asks is how to distinguish intravascular hemolysis secondary to a pathological hemolytic process from ex vivo hemolysis caused by improper specimen management. While the plasma hemoglobin measurement may reduce redraw frequency, it can’t distinguish between intravascular and ex vivo hemolysis. Plasma haptoglobin, potassium, and LDH can. Intravascular hemolysis consumes haptoglobin, so a normal haptoglobin level implies ex vivo hemolysis. Ex vivo hemolysis generates markedly elevated potassium and LDH, whereas in intravascular hemolysis, the potassium and LDH may be partially cleared.

Your comments, as always, are welcome.

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