Preanalytic Errors

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Preanalytic Errors

Table 4. Examples of Preanalytical Errors and their Effects.
Preanalytical ErrorWhat is it?How does it happen?What is the result?
Hemolysis Red blood cells (RBCs) break and release contents of cell into plasma.
  • Needle incorrectly positioned in vein; cells forced to squeeze through opening.
  • Needle gauge too small; slow blood return into tube.
  • Vigorous mixing or shaking of tube.
  • Alcohol on skin that has not had sufficient time to dry.
  • Some test results may be falsely elevated. (Potassium is especially affected by hemolysis.)
  • Patient may have to be re-drawn.
Clotted specimen Clumped or clotted cells in specimen that requires anticoagulated or whole blood
  • Insufficient mixing of blood with anticoagulant in tube.
  • Delay in mixing tube.
  • Slow filling tube.
  • Inaccurate test results for cell counts and clotting studies.
  • Patient may have to be re-drawn.
Tube filled to incorrect volume Too little or too much blood in tube.
  • Tube removed from needle too quickly.
  • Vacuum in tube has been compromised due to use of tube past the expiration date (Results in a short fill).
  • Manual fill of tube may lead to over-fill.
  • Test results may be unreliable due to dilution errors.
  • Patient may have to be re-drawn.