Anemia is present in adults if the hematocrit (the ratio of the volume occupied by packed red blood cells to the volume of the whole blood as measured by a hematocrit) is less than 41 per cent (hemoglobin < 13.5 g/dL) in males or less than 37 per cent (hemoglobin < 12 g/dL) in females.

Congenital anemia is suggested by the patient's personal and family history. Poor diet results in folic acid deficiency and contributes to iron deficiency in adults.

Physical examination includes attention to signs of primary hematologic diseases (lymphadenopathy, hepatosplenomegaly, or bone tenderness).

Anemias are classified according to their physiologic basis i.e. whether related to diminished production or accelerated loss of red blood cell, or according to cell size.

The diagnostic possibilities in microcytic anemia of chronic disease. A severely microcytic anemia (mean cell volume [MCV] < 70 fL) is due to either iron deficiency or thalassemia (an inherited form of anemia caused by faulty synthesis of hemoglobin).

Macrocytic anemia may be due to megaloblastic (folate or Vitamin B12 deficiency) or nonmegaloblastic causes, in particular myelodysplasia and the use of antiretroviral drugs.

A severely macrocytic anemia (MCV > 125 fL) is almost always megaloblastic; exceptions are the myelodysplastic syndromes.

Iron deficiency anemia:

Iron deficiency is the most common cause of anemia worldwide. Iron is necessary for the formation of heme and other enzymes.

Total body iron ranges between 2 and 4 g: approximately 50 mg/kg in men and 35 mg/kg in women. Most (70 - 95 per cent) of the iron is present in hemoglobin in circulating red blood cells.

One millimeter of packed red blood cells (not white blood) contains approximately 1 mg of iron. In men, red blood cell colume is approximately 30 mL/kg.

A 70-kg man will therefore have approximately 2,100 mL of packed red blood cells and consequently 2,100 mg of iron in his circulating blood. In women, the red cell volume is about 27 mL/kg; a 50-kg woman will thus have 1350 mg of iron circulating in her red blood cells.

Only 200-400 mg of iron is present in myoglobin (a hemoprotein that receives oxygen from hemoglobin and stores it in the tissues until needed) and nonheme enzymes.

Aside from circulating red blood cells, the major location of iron in the body is the storage pool, as ferritin (a protein containing 20 per cent iron that is found in the intestines and liver and spleen; it is one of the chief forms in which iron is stored in the body) or as hemosiderin (a granular brown substance composed of ferric oxide; left from the breakdown of hemoglobin; can be a sign of disturbed iron metabolism) and in macrophages (a large phagocyte; some are fixed and other circulate in the blood stream).

The range for storage iron is wide (0.5 - 2 g); approximately 25 per cent of women in India have none.

In an average diet containing 10-15 mg of iron per day, about 10 per cent of their amount is absorbed.

Absorption occurs in the stomach, duodenum and upper jejunum. Dietary iron present as heme is efficiently absorbed (10-20 per cent) but nonheme iron less so (1-5 per cent), largely because of interference by phosphates, tannins and other food constituents.

Small amounts of iron - approximately 1 mg/d - are normally lost through exfoliation of skin and mucosal cells. There is no physiologic mechanism for increasing normal body iron losses.

Menstrual blood loss in women plays a major role in iron metabolism. The average monthly menstrual blood loss is approximately 50 mL or about 0.7 mg/d.

However, menstrual blood loss may be five times the average. To maintain adequate iron stores, women with heavy menstrual losses must absorb 3-4 mg of iron from the diet each day.

This strains the upper limit of what may reasonably be absorbed and women with menorrhagia of this degree will almost always become iron deficient.

Treatment:

The diagnosis of iron deficiency anemia can be made either by demonstrating an iron deficient state or by evaluating the response to a therapeutic trial or iron replacement.

Ferrous sulfate, 325 mg three times daily which provides 180 mg of iron daily of which up to 10 mg is absorbed (though absorption may exceed this amount in case of severe deficiency), is the preferred oral therapy.

Compliance is improved by introducing the medicine more slowly in a gradually escalating does with food.