Hi there. In anemia, a complete blood count may reveal a low no. of RBCs. A reduced average size of red cells ( mean corpuscular volume) and reduced amount of hemoglobin within RBC ( mean corpuscular hemoglobin) may be noted. Microscopic examination of a bloodsmear reveals reduced or enlarged size of red cells ( microcytic or macrocytic RBC), deformed RBC such as the elongated sickle cell, or RBC fragments ( schistocytes). Other findings are low hemoglobin concentration and/or a low hematocrit. CBC results and information related to the size and appearance of the RBC provide clues as to the cause of anemia and what tests to perform next.
Tests for iron include ferritin, serum iron, total iron binding capacity (TIBC). These tests differentiate iron deficiency anemia from other types of anemia involving iron such as sideroblastic anemia and anemia due to chronic disease.
Blood tests for folate and vitamin B12 differentiate between folate deficiency and vitamin B12 deficiency ( pernicious anemia). In some cases, a Schilling’s test is needed to further study vitamin B12 deficiency. Levels of methymalonic acid and homocysteine can confirm B12 deficiency. Disorders of hemoglobin e.g. thallesemia, sickle cell anemia can be confirmed with hemoglobin electrophoresis.
Also a therapeutic trial can be used to diagnose a nutritional anemia. Iron replacement therapy is given for suspected case of iron deficiency. Vitamin B12 is given to detect B12 deficiency and folate for folate deficiency anemia. The diagnosis is made if improvement is seen after the therapy. Hope this makes sense. Take care.