1. SECTIONS:
2. preface & acknowledgements
3. genetics at a glance
4. contacts, support & testing
5. testing & pregnancy
6. newborn screening
7. cancer in the family
8. cardiovascular conditions
9. chromosomal conditions
10. clotting & bleeding conditions
11. cystic fibrosis
12. diabetes
13. fragile X syndrome and other causes of developmental delay
14. haemoglobinopathies
15. hereditary haemochromatosis
16. neurofibromatosis
17. neurological conditions
18. psychiatric conditions
19. genetics in practice
20. emerging genetic technologies
21. glossary

Haemoglobinopathy testing

1. Haemoglobinopathy testing determines the types, quantity and proportions of haemoglobin in the blood. Techniques for this may include haemoglobin electrophoresis and High Pressure Liquid Chromatography (HPLC) analysis. Blood films and HbH (see Genetics, under α-thalassaemia) preparations identify HbH inclusions found in HbH disease and in carriers for two-gene deletion
   α-thalassaemia (--/ α α or -α/-α).
   
2. Ideally, haemoglobinopathy testing should be performed six months after iron replacement and when iron stores are replete. However, testing should not be delayed if the woman is pregnant. If the woman is pregnant and has low red cell indices, her partner should be investigated.
   
3. Consult a haematologist or thalassaemia service for advice.
   
4. In general, haemoglobinopathy testing should be performed after FBE and ferritin investigations.

 

Haemoglobinopathy testing should be performed concurrently with FBE/ferritin for:

1. Pregnant woman with low red cell indices
   
2. Pregnant woman from a high-risk ethnic background
3. Partners of the pregnant woman should be tested at the same time as the pregnant woman
4. Partners of individuals who are carriers for thalassaemia or a haemoglobin variant
   
5. A family history of haemoglobinopathy or haemoglobinopathy carrier state
   
6. Individuals from ethnic groups with a high prevalence of haemoglobinopathy
   
7. Consanguinity

 

Interpretation of results

1. A haematologist or thalassaemia service should be consulted for assistance in interpreting haemoglobinopathy testing results, as interpretation is influenced by the clinical picture.
   
2. β-thalassaemia carrier state is characterised by the presence of increased HbA2, but this can be masked in some circumstances, such as low iron stores.
   
3. α-thalassaemia carrier states are characterised by low red cell indices, with normal HbA2 and/or haemoglobin electrophoresis results. Individuals with a three-gene deletion and two-gene deletions may be identified by presence of HbH bodies on HbH preparation; however, a normal HbH preparation does not exclude α-thalassaemia carrier state, especially one-gene deletion forms where the MCV & MCH are also usually in the normal range.
   
4. Definitive identification of α-thalassaemia with one- and two-gene deletions requires DNA testing.

 

Figure 2

Suggested protocol for targeted carrier testing of high risk populations 1 for patients in
ANY ONE of the categories below:

 

Table 1

Interpretation of haemoglobinopathy carrier testing results

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