packed cell volume (PCV)
The portion of whole blood
volume occupied by erythrocytes (red
blood cells). Packed cell volume (PCV) has traditionally been determined
by measuring the height of the red cell volume in a micro-hematocrit capillary
filled with whole blood, after centrifugation (see diagram). PCV is a directly
measured value, whereas the hematocrit
(Hct) is the corresponding calculated value, calculated by multiplying a
red blood cell count (RBC count) with the mean erythrocyte volume (MCV).
For most practical purposes PCV and Hct are interchangeable (and are frequently
used as such by many authors), but typically PCV is slightly higher than
the more accurate Hct due to plasma trapping (between the packed cells in
a centrifuged capillary).
Source: Laboratory for Applied Biotelemetry & Biotechnology,
Dept of Marine Biology at Texas A&M University Galveston