The mean corpuscular volume (MCV) is one of the standard red blood cell "indices" (table 1). It is the volume of the "average" red blood cell, stated in femtoliters (fL). Measurement of the MCV and its importance in the differential diagnosis of anemia will be discussed here . Control of red blood cell hydration, which directly influences the MCV, is discussed separately. (See "Control of red blood cell hydration".)
A general approach to the patient with anemia is presented separately. (See "Approach to the adult patient with anemia".)
METHODOLOGY AND NORMAL VALUES
The MCV can be measured or calculated in a number of different ways (see "Automated hematology instrumentation"):
- Use of volume-sensitive automated blood cell counters, such as the Coulter counter. In this type of apparatus, the red cells pass one-by-one through a small aperture and generate a signal directly proportional to their volume.
- Other automated counters measure red blood cell volume by means of techniques that measure refracted, diffracted, or scattered light
- By calculation from an independently-measured red blood cell count (RBC) and hematocrit (Hct), as follows:
MCV (femtoliters) = 10 x Hct (percent) ÷ RBC (millions/microL)