MCV blood test
MCV (Mean Corpuscular Volume) blood test measures the size of RBC. Any change in the size of RBCs indicates certain disorders. This test is often conducted along with RDW blood test. With MCV blood test, RBCs can be categorized into normal, small or large sizes. Larger cells are usually indicative of macrocytic anemia. On the other hand, those with small cells may suffer microcytic anemia. Larger RBCs may indicate liver disease, hypothyroidism, folic acid or vitamin B12 deficiency or marrow aplasia. Decreased size of red blood cells is usually noticed in persons suffering from anemia, thalassemia, lead poisoning or chronic renal failure.
MCV Blood test range
MCV blood test is done using electrical impedance or light deflection. The MCV values are considered as significant and reliable in the clinical correlation of a disease. The standard reference value for MCV is 80-100 femolitres. The reference range varies from person to person depending on the age group. In children the reference range for MCV is given in three categories:
For Newborns (95 to 121 fl)
For Infants and Toddlers (76- 86 fl)
For Teenagers (boys: 78- 98 fl and girls 78-102fl)
For Adults 98fl
The MCV in association with underlying anemic conditions is determined by the following mathematical formulae:
MCV = 10 X (packed cell volume / RBC count)
Mentzer index
Mentzer index is mathematically expressed as MCV / RBC count. The Mentzer index value determines conditions such as thalassemia when the ratio is less than 13 and it indicates iron deficiency anemia when the ratio is greater than 13.
RDW blood test
RDW (Red cell distribution width) blood test that calculates any variation in size of RBC. Normally Red Blood Cells are of a standard size. Since RBCs tend to get smaller and rounder as they age, it is not possible for all cells to be exactly the same size. RDW test determines the changes in the volume of the cells in the red cell population. The variations pertaining to the size of the red blood cells is called Anisocytosis and the shape is called Poikilocytosis.
The incidence of these conditions and the detection of abnormal or varied red blood size are determined by diagnostic blood smear analysis and also through automated analyzers.
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Calculating Red Blood Cell Distribution: The determination of red cell distribution width is mathematically expressed as
Red cell distribution width = (Standard deviation ÷ Mean cell volume) X 100.
Conditions such as pernicious anemia cause changes in RBC size. Often there is variation in shape too. This can be detected by changes in RDW. Normal RDW range is 11 - 15%. Higher RDW is indicative of disorders such as anemia. RDW blood test is often conducted along with MCV blood test to check the exact cause.
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Bibliography / Reference
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