16: HAEMATOLOGY

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CHAPTER 16 HAEMATOLOGY

Haemoglobinopathies

ANAEMIA

Patients with anaemia are diagnosed because they look anaemic, have the symptoms of anaemia or are found incidentally to be anaemic.

Diagnosis

History.

• Bleeding: heavy periods are a common cause of iron-deficiency anaemia. Rectal bleeding is the other common cause.

• Diet: the elderly often take a diet low in iron. Vegetarians are also at risk.

• A past history of iron-deficiency anaemia, which raises the chance of another episode of the same.

• Symptoms of anaemia: tiredness, breathlessness, exhaustion and palpitations can all be caused by anaemia. Angina can be unmasked or exacerbated by becoming anaemic.

• Symptoms occasionally accompanying anaemias: bruising and infections suggest aplastic anaemia. Paraesthesia of the feet can occur in pernicious anaemia. Chronic disease can cause anaemia, e.g. renal failure, inflammatory bowel disease and rheumatoid arthritis. Cancer often causes anaemia.

Examination.

In general practice there is usually little to add by examining the asymptomatic patient other than to look at the conjunctivae for pallor. The yellowish appearance of the face in pernicious anaemia is characteristic.

Investigations

• Full blood count: the first test is the FBC and film. This alone is sufficient to confirm the presence of anaemia, which is characterised by a Hb less than:

– 12.5 g/dl for men

– 11.5 g/dl for women.

• Iron-deficiency anaemia is characterised by a low mean cell volume (<76 fl) and a low mean cell Hb concentration (<30 g/dl), and should be confirmed by checking for a low serum iron (<15 μmol/l in men; 14 μmol/l in women).

• Transferrin: a high transferrin (>400 mg/dl) supports the diagnosis of iron-deficiency anaemia. A low transferrin (<200 mg/dl) suggests the anaemia of chronic disease.

Where there is no obvious cause for the anaemia (e.g. heavy periods), the patient should be referred, if appropriate, for investigation of the gastrointestinal tract. Occult malignancy occasionally comes to light after presenting with anaemia.

Management

Iron-deficiency anaemia

Mild anaemia (Hb >7 g/dl) can be treated with ferrous sulphate tablets 200 mg daily, rechecking the full blood count after 1 month. Attention should be given to the underlying cause, i.e. dietary advice or treatment of menorrhagia.

Some patients cannot tolerate ferrous sulphate tablets due to gastrointestinal side-effects. Try ferrous fumarate in these cases. If oral iron fails to correct the anaemia, or if tablets cannot be tolerated, use iron for injection. (See Data Sheet Compendium, published by Datapharm, at www.emc.medicines.org.uk/.)

Patients with severe anaemia (Hb <7 g/dl) who are symptomatic should be considered for blood transfusion in hospital.

Anaemia of chronic disease

Many chronic diseases are accompanied by a mild anaemia with an Hb of around 10 g/dl. These patients are usually asymptomatic from the anaemia and require no treatment as such. In fact, their anaemia is often refractory to treatment.

Macrocytic anaemia

Treatment is of the underlying cause, as identified above.

Vitamin B₁₂ deficiency is usually due to pernicious anaemia, malabsorption of B₁₂ from the gut (due to e.g. inflammatory bowel disease) or dietary deficiency. Check with a blood test for the presence of intrinsic factor antibodies. A positive result is strongly suggestive of pernicious anaemia.

Treat with intramuscular hydroxocobalamin 1 mg every 3 days for 2 weeks, then once every 3 months for life. Check an FBC after 1 month to make sure the macrocytosis has gone and to exclude iron-deficiency anaemia, which may complicate B₁₂ treatment.

Folate deficiency is usually caused by malabsorption due to bowel disease, but rarely it is caused by dietary deficiency. Treatment is with oral folic acid 5 mg daily. Vitamin B₁₂ deficiency should be excluded prior to commencing treatment with folic acid, as peripheral neuropathy in B₁₂ deficiency can be precipitated by the administration of folate.

Anaemia of pregnancy.

Other causes of anaemia.

Other anaemias should be investigated and treated by referral to the haematology outpatient department.

HAEMOGLOBINOPATHIES

Screening.

In general practice, patients with anaemia should be screened for thalassaemia and sickle cell traits if they are from Mediterranean, South-East Asian or Afro-Caribbean races.

Investigations.

Blood should be sent for haemoglobin electrophoresis. Most results are normal, but mild abnormalities commonly demonstrate thalassaemia or sickle cell traits. These usually cause no more than a mild, asymptomatic anaemia and a slightly reduced mean cell volume and mean cell haemoglobin.

Counselling.

Consider referral for genetic testing and counselling if the patient is contemplating starting a family. Refer to a department of clinical genetics.

Sickle cell disease

Homozygous sufferers should have specialist involvement from a haematology outpatient department.

Be alert for a sickle crisis:

• painful swelling of the hands and feet

• rapid enlargement of the spleen

• acute fall in haemoglobin.

If suspected, admit the patient.

SPLENECTOMY

Patients without a functioning spleen have a 12-fold increased risk of infection from Pneumococcus, Haemophilus influenzae, Neisseria meningitidis and malaria compared with people with a normal spleen.

Related

Churchills Pocketbook of General Practice