MCV of <80 fL = microcytic
IDA is the most common cause
Check Mentzer index: (MCV/RBC count)
A Mentzer index >13 suggests iron deficiency, whereas a result <13 correlates with thalassemia
In iron deficiency, the marrow cannot produce as many RBCs and they are small (microcytic), so the RBC count and the MCV will both be low, and as a result, the index will be greater than 13. Conversely, in thalassemia, which is a disorder of globin synthesis, the number of RBCs produced is normal, but the cells are smaller and more fragile. Therefore, the RBC count is normal, but the MCV is low, so the index will be less than 13.
Both IDA and ACD has low serum iron level.
However, IDA is associated with increased TIBC, which measures the unbound sites on transferrin.
Iron divided by TIBC equals transferrin saturation.
In chronic disease (ACD), serum iron is low, because iron is trapped in storage. That's why the ferritin, or stored iron, is elevated and normal or low TIBC.
Sideroblastic anemia is the only form of microcytic anemia in which the circulating iron level is elevated.
Thalassemia = normal to high serum iron and ferritin and transferrin saturation is high
IDA
Causes
Infants - breastfeeding
Child - poor diet
Adult - PUD, menses, pregnancy
elderly - poor diet, colon polyps/ca, infection (intestinal worms)