ABSTRACT
In both methods, the length of the red cell column after centrifugation relative to the total length of the column gives the PCV reading. The manually spun PCV is affected by several variables, including trapped plasma, white cell and platelet contamination of the red cell layer, indistinct margin between red and white cell layers, nonflat tube seals, red cell dehydration, and the oxygenation state of the red cells. Fortunately, these biases counterbalance each other so the net error in the PCV is small, <1 PCV unit. Even this small error can have wide-reaching consequences when applied globally, although it has little impact on the individual patient. For example, an error of 1 PCV unit can lead to the rejection of up to 3.5% potential blood donors. In this context, PCV errors of this magnitude are unacceptable. There is a clear need for an unbiased reference method for the PCV to validate working methods. Several methods have been proposed, but they are complex, time consuming, and may require radiolabeled reagents that are difficult to obtain and may require special licensing before use. The ICSH (International Council for Standardization in Hematology) Expert Panel on Cytometry recommends a hemoglobin/ MCHC-based reference method that eliminates all six errors listed previously.
