Haemoglobin disorders and anaemia
A fall in the concentration of haemoglobin below the reference level for the age and sex of the individual.
Anaemia is usually due to a fall in haemoglobin; rarely it may result from a rise in plasma volume, e.g. in fluid overload or during pregnancy. Anaemia is usually classified according to the size of the red blood cells (see Fig. 12.2).
Symptoms suggestive of anaemia include fatigue, faintness, headaches, breathlessness, angina of effort, intermittent claudication and palpitations. On examination there may be pallor, tachycardia, a systolic flow murmur and/or cardiac failure.
The cause of anaemia must always be found. Initial investigations must include a full blood count and blood film.
These provide information on the degree of anaemia, whether the disorder is confined to haemoglobin or whether it includes abnormalities of white blood cells and/or platelets. The full blood count also provides information on the mean corpuscular volume (MCV) to guide further investigations. The blood film demonstrates the morphology of red blood cells, white blood cells and platelets.
· In microcytic anaemia, a serum iron and ferritin, and total iron binding capacity (TIBC) are measured to assess iron stores.
· In macrocytic anaemia with normal vitamin B12 and folate levels, or in suspected haematological malignancy, a bone marrow aspiration and trephine is usually performed.