Iron Deficiency Anaemia
Iron deficiency anaemia is the most common cause of anaemia. Symptoms are related to the overall decrease in number of red blood cells and/or level of haemoglobin. The most common signs and symptoms include:
- feeling of tiredness, fatigue
- lack of energy
Symptoms that are typical of iron deficiency and which may appear as iron stores in the body decrease may include brittle or spoon-shaped nails, swollen or sore tongue, cracks or ulcers at the corners of the mouth (“angular cheilosis”) or a craving to eat unusual non-food substances such as ice or dirt (also known as “pica”).
Iron is an essential trace element and is necessary for the production of healthy red blood cells (RBCs). It is one component of haem, a part of haemoglobin, the protein in RBCs that binds to oxygen and enables RBCs to transport oxygen throughout the body. If not enough iron is absorbed by the body, then iron that is stored in the body will be used up. If iron stores are low then fewer red blood cells are made and they have decreased amounts of haemoglobin in them which results in anaemia.
Some of the causes of iron deficiency include:
- Bleeding—if bleeding is excessive or occurs over a period of the time (chronic), the body may not take in enough iron or have enough stored to produce sufficient haemoglobin and/or red blood cells to replace what is lost. In women, iron deficiency may be due to heavy menstrual periods, but in older women and in men, the bleeding is often from disease of the stomach or intestines such as ulcers and cancer.
- Dietary deficiency—iron deficiency may be due simply to not eating enough iron in the diet. In children and pregnant women especially, the body needs more iron, Pregnant and nursing women frequently develop this deficiency since the baby requires large amounts of iron for growth. Lack of iron can lead to low birth weight babies and premature delivery. Pre-pregnant and pregnant women are routinely given iron supplements to prevent these complications. Babies who are taking milk from anaemic mothers tend to have iron deficiency anaemia as well.
- Absorption problem—certain conditions affect the absorption of iron from food in the gastrointestinal (GI) tract and over time can result in anaemia. These include, for example, coeliac disease, Crohn’s disease, lack of acid in the stomach (“achlorhydria”) or previous surgery to remove part of the bowel
Initial blood tests typically include a full blood count (FBC). Results may show:
- Haemoglobin (Hb)—may be normal early in the disease but will fall as the anaemia worsens
- Red blood cell indices—early on, the RBCs may have a normal size and color (normocytic, normochromic) but as the anaemia progresses, the RBCs become smaller (microcytic) and paler (hypochromic) than normal.
- Average size of RBCs (MCV)—may be decreased
- Average amount of Hb in RBCs (MCHC)—may be decreased
- Increased variation in the size of RBCs (red cell distribution width or “RDW”)
A blood film may reveal RBCs that are smaller and paler than normal as well as RBCs that vary in size (anisocytosis) and occasionally in shape (poikilocytosis). Abnormally shaped red cells may include target cells and pencil cells. The blood film may also give clues to causes of inflammation. For example it might show signs of an underactive spleen, which can be due with coeliac disease, in which iron is sometimes not absorbed well.
If your doctor suspects that your anaemia is due to iron deficiency, they may request several additional tests to confirm the iron deficiency. These may include:
- Serum iron—the level of iron in your blood; the result is usually decreased. It is important that patients fast before a serum iron blood test or the result may be misleadingly high.
- Total iron-binding capacity (TIBC) or Unbound iron-binding capacity (UIBC)—measurement of the protein (transferrin) that carries iron through the blood will be increased.
- Transferrin saturation index (ratio of serum iron to iron binding capacity). A result less than 15% may indicate iron deficiency.
- Ferritin—reflects the amount of stored iron in your body and is usually low in anaemia. Ferritin is considered to be the most specific for identifying iron deficiency anaemia, unless infection or inflammation are present
All blood tests for iron may be influenced by other illnesses or factors and they should be interpreted with caution. Sometimes they clearly indicate iron deficiency, sometimes they are unclear and sometimes they can be misleading and unhelpful.
Rarely, if your doctor is unsure whether or not you have iron deficiency anaemia and wants to be sure, they may even request a bone marrow aspirate to look directly at your iron stores. Absence of iron in a good quality bone marrow sample proves iron deficiency. Bone marrow aspirates are quickly performed and very safe, but uncomfortable and thankfully your doctor will only very rarely request this test.
If the iron deficiency is thought to be due to abnormal blood loss, such as chronic bleeding from the intestine, then other tests and procedures may be performed including a referral for colonoscopy to look and see if blood is being lost into the intestine.
A test for Helicobacter pylori may detect a bacterium that can cause ulcers in the GI tract which may be a cause of chronic bleeding. Blood tests showing antibodies to Helicobacter may be misleading however and examination of the faeces for the bacterium (faecal Helicobacter antigen testing) may be used instead.
If any of these tests are positive or if it is strongly suspected a GI bleed exists, then procedures such as endoscopy or colonoscopy may be done to find the location of the bleeding so that it can be treated.
Treatment of iron deficiency typically involves iron supplements. These are usually given by mouth. In patients intolerant of iron supplements or who can not absorb iron, it can be replaced by using intravenous infusion. If iron-deficiency is suspected to be due to abnormal blood loss, further testing is often required to determine the reason for the bleeding. When the underlying cause is found and treated then the anaemia usually resolves.
Some forms of haemolytic anaemia can lead to iron deficiency.