The thalassaemia are recessively inherited haemoglobin disorders with profound implications for individuals, families, and health services. In the United Kingdom they occur mainly in certain minority ethnic communities, but prevalence varies within these communities. Around 3-10% of Indians, 4.5% of Pakistanis, 8% of Bangladeshis, 17% of Cypriots, 0.5-1% of Afro-Caribbean’s, and 0.1% of the indigenous British carry thalassaemia. Carrier couples have a one in four chance in every pregnancy of having a child with a major thalassaemia. Unlike some other genetic disorders, the thalassaemias are common and manageable, requiring, as a minimum, regular blood transfusions and iron chelation treatment to prevent iron overload.
Uptake of early prenatal diagnosis by informed couples at risk for thalassaemia is high: when counseled in the first trimester over 90% of British Cypriots and over 70% of British Indians and Pakistanis request prenatal diagnosis. Informing couples later in pregnancy leads to lower uptake of prenatal diagnosis by British Pakistanis. With optimal carrier screening and counseling, this high uptake should be reflected in the number of prenatal diagnoses actually done, but the national audit showed that this is the case only for British Cypriots. Only 50% of Indian couples at risk and 33% of Pakistani couples actually had a prenatal diagnosis, the proportion for Pakistanis ranging from 0% to 60% by regional health authority.
What underlies these discrepancies, and what can be done about them? Cypriots are distinguished from other groups by a high level of awareness of thalassaemia among health workers and the community. Historically, thalassaemia major has been seen as a problem for Mediterranean populations, and concerted awareness campaigns have greatly reduced its birth prevalence in the Mediterranean area. For example, in Cyprus there are now almost no new affected births. The messages from the intensive Cypriot education campaign have washed over to the UK and have been reinforced by support groups and local health services. Most British Cypriots request carrier testing before marriage or in early pregnancy, so community awareness reinforces health workers’ awareness. Though prenatal diagnosis is available in India and Pakistan, there have been no education campaigns in these countries that might raise community awareness in the United Kingdom. Health workers are usually not aware that Asians are at risk of thalassaemia. The recently completed thalassaemia module of the Royal College of Physicians’ confidential inquiry into counseling for genetic disorders has shown that many districts with a large Asian population have inadequate screening policies, so that risk is often not identified or is identified too late in pregnancy for prenatal diagnosis to be acceptable. Hence most new thalassaemic births are now among the British Asian community.
Clearly, increased awareness among health workers and populations at risk is required for services to improve. In particular, primary health care providers need to become more involved in screening and counseling for haemoglobin disorders than they are at present.