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Chapter 12: Haemoglobin disorders and anaemia 467

Autografts (frozen haemopoetic progenitors from the tests (usually if there is a history of anaphylaxis) can
patient) is not associated with GVHD or GVL and may be helpful. True identification may require food chal-
involve re-infusion of leukaemic cells. However, they lenges with the patient blinded to the food being
have the advantage of availability. Peripheral stem cell tested, as there may be a psychological component
transplants are now used more frequently than autolo- to presumed food allergies.
gous bone marrow transplantation. They have the ad- Othertestsincludeimmunoglobulinandcomplement
vantage that more progenitor cells are collected and thus measurements and blood eosinophil counts.
rescue from pancytopenia occurs more rapidly.
Haemoglobin disorders
Allergy testing
and anaemia
Allergy testing most commonly involves skin prick tests
and may include the radioallergosorbent test (RAST) Anaemia
and rarely diagnostic allergen challenge. The choice of
testisdependentonthesuspectedallergenandthenature Definition
of any previous allergic reaction. Testing of patients with A fall in the concentration of haemoglobin below the
a history of anaphylaxis may be confined to RAST and reference level for the age and sex of the individual.
should only be undertaken by an allergy specialist.
Skin prick tests allow the testing of multiple allergens
Aetiology
simultaneously. Small amounts of a specific suspected Anaemia is usually due to a fall in haemoglobin; rarely
allergen or a panel of common allergens is applied to it may result from a rise in plasma volume, e.g. in fluid
the skin, which is then pricked to allow the allergens to overload or during pregnancy. Anaemia is usually clas-
penetratetheskin.Anerythematousreactionfollowed sified according to the size of the red blood cells (see
by aweal occurs within minutes when positive. The Fig. 12.2).
testisreadat15minutesandawealdiameterof≥3mm
Clinical features
is normally considered positive. Skin tests are useful
Symptoms suggestive of anaemia include fatigue, faint-
in detection of respiratory allergies, food allergies and
ness, headaches, breathlessness, angina of effort, inter-
allergies to penicillin and insect bites. Patients should
mittent claudication and palpitations. On examination
not be taking antihistamine medication at the time of
there may be pallor, tachycardia, a systolic flow murmur
the test.
and/or cardiac failure.
RAST measures specific IgE antibodies in the blood to

individual allergens. Investigations
Food allergies can normally be diagnosed on a good Thecauseofanaemiamustalwaysbefound.Initialinves-

clinical history. If doubt exists skin prick tests or RAST tigations must include a full blood count and blood film.
Reduced Haemoglobin

Microcytic Anaemia Normocytic Anaemia Macrocytic Anaemia
(small red blood cells) (normal sized red blood cells) (large red blood cells)
MCV <80 fI MCV 80–95 fI MCV >95 fI
Iron deficiency anaemia Acute blood loss Liver disease, Alcohol,
Thalassaemia Anaemia of chronic disease Haemolysis, Myelodysplasia
Sideroblastic anaemia Infection, Malignancy B or folate deficiency
12

Figure 12.2 Important causes of anaemia.