Internally Peer Reviewed When considering back up equipment, the hematocrit centrifuge is probably the most useful. The packed cell volume is determined by centrifuging the specimen in capillary tubes and measuring the height of the red cell column. A short EDTA sample will have an increased anticoagulant to red cell ratio, which causes the red cells to shrink and the hematocrit to be falsely decreased. For EDTA samples use blue banded, plain capillary tubes.
Traditional tubes are glass and unplugged.
Mylar coated tubes, plastic tubes, and pre-plugged tubes are available. Plastic pre-plugged tubes are a good choice. They decrease the risk of breaking a tube and puncuturing the finger of the person performing the test and avoid some sources of error. Tilt each tube so that the blood is near the colored band. Hold the tube horizontally and wipe all of the excess blood off of the tubes before it dries.