The hematocrit is the ratio of the red blood volume to the volume of whole blood. A close relationship exists between hemoglobin and hematocrit which can be used if only one value is available or for quality control. In automated hematologic analyzers, the hematocrit is not directly measured. Rather, it is calculated from the red blood cell count and MCV, which are measured.


Estimating Hematocrit from Hemoglobin Concentration


estimated hematocrit (percent) =

= ((hemoglobin in g/dL) * 2.8) + 0.8



• Hemoglobin is in g/dL.




hemoglobin in g/dL =

= (hematocrit - 0.8) / 2.8 =

= (0.357 * (hematocrit in percent)) - 0.286


A low or high MCV does not distort the relationship expressed in the equation, although this had been an issue of concern.


An alternative equation for the hematocrit is:


estimated hematocrit (percent) =

= (hemoglobin in g/dL) * 2.941



• 2.941 = ((100 g/dL) / (normal MCHC = 34 g/dL))


Estimating Hematocrit from RBC and MCV


hematocrit =

= RBC * MCV / 10


This calculation can be used to validate a questionable test result if the other 2 parameters are known with confidence.


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