Theoretically, measuring each red cell and adding those volumes to get a total red cell volume is the most accurate method.
Centrifuged hematocrits have a built in bias due to the trapped plasma.
When red cells have very abnormal shapes, this trapped plasma may be increased enough to cause a significant change in the centrifuged hematocrit. Some studies have shown that the two methods show better correlation if K2EDTA is used as the anticoagulant. Understanding how the automated hematocrit is derived is very important when trouble shooting or using back up methods such as a centrifuged hematocrit. If a centrifuged hematocrit is substituted for an automated value, the MCV must be manually calculated. All rights reserved.