Iron deficiency anaemia is one of the most common haematological conditions in the world, affecting females of childbearing age, children and individuals living in low- and middle- income countries.
Iron is an essential component for haemoglobin synthesis, and its uptake, storage and utilisation are regulated by a number of physiological mechanisms. Haemoglobin carries oxygen from the lungs to the rest of the body. Iron is absorbed in proximal small intestine via dietary containing iron. Food containing high iron such red meats, fruits and vegetables such as beans, lentils, tofu and etc. To increase iron absorption, Vitamin C can be consumed with iron tablets or foods containing high iron.
The major cause of iron deficiency in resource-rich countries is blood loss, either overt or occult. Gastrointestinal or urogynaecologic sources are common.
Overtbleeding is caused by:
- Traumatic haemorrhage
- Hematemesis or melena
- Heavy menstrual bleeding
- Pregnancy or delivery
Other causes of blood loss are:
- Frequent blood donation
- Excessive diagnostic blood testing
- Occult bleeding, typically gastrointestinal (eg. gastritis, malignancy, angiodysplasia) but may also include haemolysis with urinary losses
- Exercise-induced blood loss, often due to occult gastrointestinal bleeding
- Gastrointestinal parasites (hookworm, whipworm)
The WHO defines anaemia as <130g/L for men, <120g/L for women and <110g/L in pregnant women and preschool children. Anaemia with low mean corpuscular volume (MCV) or mean corpuscular haemoglobin (MCH) is commonly due to iron deficiency.
Many people do not have clinically significant symptoms, and iron deficiency is often diagnosed on routine screening, or in the setting of investigation for causes of anaemia or blood loss.
Children may present with decreased school productivity and and impaired cognitive development. Adults may present with non-specific symptoms such as headaches, fatigue and weakness and reduced exercise tolerance.
Iron replacement is the mainstay of treatment of iron deficiency anaemia, and choice of modality should be determined by clinical indication.
Oral iron replacement is inexpensive, non-invasive and effective when given at adequate doses. Adults will need 100-200mg of elemental iron and children will need 3-6mg/kg. Higher doses of iron may precipitate more side effects,commonly gastrointestinal. With therapeutic doses of oral iron, haemoglobin levels should rise by above 20g/L every three weeks. After normalisation of haemoglobin, it is reasonable to continue treatment for 3-6 months in adults and 2-3 months in children, as long as therapy is well tolerated, in order to replenish iron stores. Ascorbic acid (vitamin C) deficiency may be a cause of lack of response to iron therapy. Co-administration may aid absorption, and as such there is an oral preparation that combines ferrous sulphate with ascorbic acid.
Parental iron replacement can be given in the form of an intravenous infusion given in the ambulatory care setting. While oral iron replacement aims to replenish iron stores in a number of weeks or months, parenteral iron is often given to replenish iron stores rapidly, usually in a single infusion. Intramuscular injection is often avoided, as though effective, it can be associated with pain at the injection site and permanent skin staining. Newer intravenous parenteral preparations, such as iron carboxymaltose, will allow safe transfusion over much shorter periods.
Red blood cell transfusion should be used for immediate management in patients with severe anaemia compromising end-organ vitality or function, or where iron deficiency anaemia is complicated by serious ongoing bleeding. Transfusion does not replenish iron stores, while also introducing unnecessary risks of transfusion, such as immunological and infective complications. It should always be followed by iron replacement therapy to replenished stored iron in the long term.