During manual hematocrit testing, which factor can falsely decrease the result?

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Multiple Choice

During manual hematocrit testing, which factor can falsely decrease the result?

When performing manual hematocrit, the result reflects the fraction of the capillary tube occupied by red cells after centrifugation. If the red cells become smaller before spinning, the packed cell layer is thinner and the hematocrit appears lower than it truly is. Excess EDTA can cause the red cells to crenate and shrink because high concentrations of the anticoagulant chelate calcium and disrupt cellular ion balance, pulling water out of cells. This shrinking reduces the apparent red cell volume, yielding a falsely decreased hematocrit. Other factors don’t reliably produce a consistent decrease in this measurement. Hemolysis can complicate interpretation but doesn’t predictably produce a lower packed cell volume in the microhematocrit method. Excess potassium or high ambient temperature don’t have the same direct, reproducible effect on the red cell mass used to calculate the hematocrit.

When performing manual hematocrit, the result reflects the fraction of the capillary tube occupied by red cells after centrifugation. If the red cells become smaller before spinning, the packed cell layer is thinner and the hematocrit appears lower than it truly is. Excess EDTA can cause the red cells to crenate and shrink because high concentrations of the anticoagulant chelate calcium and disrupt cellular ion balance, pulling water out of cells. This shrinking reduces the apparent red cell volume, yielding a falsely decreased hematocrit.

Other factors don’t reliably produce a consistent decrease in this measurement. Hemolysis can complicate interpretation but doesn’t predictably produce a lower packed cell volume in the microhematocrit method. Excess potassium or high ambient temperature don’t have the same direct, reproducible effect on the red cell mass used to calculate the hematocrit.

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