Hematocrit (Packed Cell Volume) Lecture Notes

Hematocrit (Packed Cell Volume) Overview

• Definition: Hematocrit (Hct), also known as Packed Cell Volume (PCV), is a measure of the proportion of blood volume that is occupied by red blood cells (RBCs).

Automated Hematocrit Testing

• Automated Results: Hematocrit results can be obtained using multiparameter instruments.
  • These automated devices compute Hct values based on individual Mean Corpuscular Volumes (MCVs) and the red cell count.
  • The results from these automated systems are unaffected by trapped plasma that may remain in the RBC column, which can otherwise skew manual measurements.

Errors in Manual Hematocrit Measurements

• Sources of Error: Manual measurements of hematocrit can be influenced by various errors:
  • Specimen Errors:
  • Inadequate filling of the EDTA tube can lead to falsely decreased Hct values due to red blood cell shrinkage.
  • Technical Errors:
  • Examples include overcentrifugation or improper sealing of the test capillary tube, both of which can lead to inaccuracies in the Hct value obtained.

Clinical Implications

• Clinical RBC Disorders: Conditions such as macrocytic anemia or sickle cell anemia can lead to falsely elevated hematocrit levels.
  • Clinicians should be wary of these disorders when interpreting Hct results, as they can misrepresent the true hematocrit when assessing patient health or diagnosing conditions.