Deficiency anaemias

'Tired all the time' may be the classic heartsink complaint but practice nurses should always consider whether it is because the patient has anaemia. In the first of a two-part article, Beverley Bostock discusses deficiency anaemias

Tiredness is a symptom that is commonly reported to clinicians working in general practice. There are many causes for people feeling tired all the time, but anaemia should always be considered. Other symptoms associated with anaemia include shortness of breath and dizziness. The term anaemia refers to a low haemoglobin level, resulting in a reduced capacity for oxygen transportation. The main underlying cause of anaemia is a problem with the erythrocytes (red blood cells), which carry oxygen around the body on carriers known as haemoglobin (Hb). Anaemia may result from the body's inability to make enough erythrocytes or haemoglobin or both; alternatively the body may be losing erythrocytes from the circulation at an accelerated rate due to blood loss or excessive breakdown of these cells.

Blood cells (erythrocytes, leucocytes and platelets) are produced in the bone marrow, through a process known as haemopoiesis. Erythropoiesis, as the name suggests, refers to the production of red blood cells. The kidneys produce erythropoietin, an essential component of healthy red blood cell production.¹ Chronic kidney disease, then, can lead to anaemia. This will be discussed further in a later article. In terms of nutrients, the body needs iron, vitamin B12 and folate to make healthy red blood cells. A deficiency of any of these can lead to anaemia.

Understanding the cause of the anaemia will help to inform the treatment decision, therefore. In this article we will examine some of the most common types of deficiency anaemia and discuss how they are diagnosed and treated.

Clinicians should therefore keep in mind the key reasons why Hb levels may be reduced:2

• Faulty synthesis of Hb
• Reduced erythropoiesis
• Excessive haemolysis (destruction of erythrocytes)
• Blood loss

Haemoglobin is made up of two parts: haem and globin. In anaemia, synthesis of either of these components may be defective. A lack of iron will affect the synthesis of haem. The lack of iron may be due to poor nutritional status (poor intake or malabsorption) or may simply be the result of the body requiring more iron than normal — such as when blood loss occurs or during pregnancy.

The definition of anaemia according to the World Health Organization is a haemoglobin (Hb) level of less than 12.5 g/dL, although this varies according to the age and sex of the individual. Children aged 6 months to 6 years may be considered anaemic if their Hb is less than 11 g/dL, whereas children aged 6-14 years are considered anaemic when Hb levels are less than 12 g/dL.

As haemoglobin is carried on the erythrocytes, anaemia may result from a drop in the number of circulating erythrocytes or a reduction in the Hb concentration. Although these will often happen together, there are occasions where they may happen independently of each other. For example, in early iron deficiency anaemia, the number of red cells is normal but they are smaller and therefore cannot carry the same amount of Hb as they should. This leads to lower concentrations of Hb. Eventually, as the anaemia progresses, the number of red cells will also drop. Looking at the size of the red cells, then, may help with the diagnosis of the type and cause of the anaemia.

IRON DEFICIENCY

Clinicians sometimes assume that a low Hb is indicative of iron deficiency anaemia. However, although a low Hb may indicate the possibility of this condition, further tests are needed to confirm the diagnosis and exclude other causes. In pregnancy, for example, a low Hb may simply be the result of an increased circulating volume, which has led to lower concentrations of Hb. It is not always easy to differentiate when low Hb levels are the result of this as opposed to a true iron deficiency anaemia of pregnancy.

Further analysis of the results from the blood count may raise further suspicions that iron deficiency is the reason for the low Hb. The blood cells may be smaller, as indicated by a reduced mean cell volume (MCV). These small cells are described as being microcytic and the cells themselves may also be pale (hypochromic). In some people the platelet count is also raised in iron deficiency anaemia.³

The best test for confirming that the body's iron stores are depleted is the serum ferritin test. If this is low, it indicates that the body's iron stores are being used up. Total iron binding capacity (TIBC) and transferrin levels are often raised in iron deficiency anaemia indicating an increase in the body's capacity for moving iron around in times of need.

The next question is to discover what has caused the iron deficiency anaemia in the first place. Although a lack of dietary intake is often the cause, it may be that chronic bleeding is leading to the loss of iron from the body. A careful history should help to draw out any symptoms which indicate bleeding, including gastro-intestinal and gynaecological symptoms; a drug history, including the use of over the counter drugs may also flag up drugs which are known to cause gastro-intestinal bleeding such as aspirin and other non-steroidal anti-inflammatory drugs. Further investigations may then be needed, such as endoscopy.

The diagnosis of iron deficiency should not be made on the basis of an abnormal blood result alone; the result should be assessed bearing in mind the history and presentation of the patient.

The treatment of iron deficiency anaemia will be based upon identifying and addressing the underlying cause, if possible. Dietary advice should be given regarding foods that are high in iron. These include:

• dark-green leafy vegetables, such as watercress and curly kale
• Iron-fortified bread
• Beans
• Nuts
• Meat
• Dried fruit e.g. apricots, prunes, raisins4

Thereafter, oral supplements may be prescribed, such as ferrous fumarate 210mg. The recommended dose for treating iron deficiency is one tablet two to three times a day; the dose advised as prophylaxis, however, is one tablet once or twice a day.⁵ Patients should be warned that this treatment may cause indigestion, dark-coloured stools which may be looser and more frequent than usual or conversely firmer and less frequent than usual. Taking iron with orange juice may increase the absorption rate.

B12 AND FOLATE DEFICIENCY

A reduction in the production of healthy red cells may be due to a lack of the nutrients required to make them or alternatively may be caused by underactive bone marrow. Key nutrients that are needed to develop healthy red cells include B12 and folate.

A lack of B12 causes some of the same symptoms as iron deficiency anaemia. B12 deficiency can result from poor dietary intake of the vitamin or it may be due to the body's inability to take it on board. A raised MCV (macrocytosis) on a full blood count may alert the health care professional to the need for a B12 and folate measurement. There are several causes for a raised MCV, however, including excess alcohol intake and thyroid disease so these should also be excluded as a possible cause. If B12 levels are found to be reduced, consideration should be given as to whether the patient has inadequate intake of B12 or whether, in fact, they are unable to absorb B12 from the digestive tract. B12 is found primarily in animal food sources, so vegans may be at risk of B12 deficiency.⁶

A further blood test should therefore be carried out to see if the patient has antibodies to 'intrinsic factor,' which enables us to absorb B12 correctly. If this test is normal, dietary assessment should be carried out. Foods rich in B12 include meat, some fish, eggs, cheese, milk and yeast extract. Oral B12 supplements may be bought over the counter; they are not available on prescription, however. If the low level is due to an inability to absorb B12 due to problems with the intrinsic factor, supplements should be given by injection as oral B12 will not be absorbed.

Other causes of low B12 readings that do not require further treatment include pregnancy and use of the oral contraceptive pill.

FOLATE DEFICIENCY ANAEMIA

B12 and folate levels are usually checked together. Low folate levels may be seen in times of increased need, such as pregnancy, or as a result of poor absorption such as in coeliac disease. If low folate levels are identified, dietary improvements can be suggested. Foodstuffs that contains high levels of folate include green vegetables such as broccoli, peas and sprouts. Oral supplements can be prescribed at 5mg/day and should be continued for at least four months, sometimes longer. Some patients may need to remain on treatment for life.

SUMMARY

In summary, then, a full blood count may provide information about Hb levels and may raise the possibility of a diagnosis of anaemia. Further examination of the blood count result may provide more evidence regarding, for example, the size of the blood cells; this may give more useful clues as to the aetiology of the problem. However, confirmation of the presence and type of the anaemia should only be made after a full assessment of the patient's signs and symptoms, if any, and once more extensive tests have been carried out. Initially these may include ferritin levels, TIBC, B12 and folate. Once the type of anaemia has been diagnosed, appropriate treatment can then begin.

COMING UP

In part 2, Beverley Bostock looks at sickle cell anaemia and types of anaemia associated with chronic diseases.

REFERENCES

1. Kelley C. Estrogen and its Effect on Vaginal Atrophy in 1.Moore G, Knight G, Blann A (2010) Haematology Oxford University Press

2.Phillips J, Murray P and Kirk P (2001) The Biology of Disease Blackwell Science Oxford

3.Galloway MJ, Smellie WS. Investigating iron status in microcytic anaemia. BMJ 2006; 333: 791-793.

4.NHS Choices (2010) Anaemia, iron deficiency — treatment Available from www.nhs.uk/Conditions/Anaemia-iron-deficiency-/Pages/Treatment.aspx Accessed July 2011

5.Electronic Medicines Compendium (2011) Fersamal — summary of product characteristics. Available at: www.medicines.org.uk/EMC/medicine/24780/SPC/Fersamal+210mg+tablets/ Accessed July 2011

6.Office of Dietary Supplements (2011) Vitamin B12 dietary supplement fact sheet. Available from http://ods.od.nih.gov/factsheets/vitaminb12/ Accessed July 2011