A National Register for Surveillance of Inherited Disorders: [Beta] Thalassaemia in the United Kingdom. (Research)

Article excerpt

Introduction

Developments in human genetic science associated with the sequencing of the human genome will greatly increase the possibilities for genetic screening and for preventing and treating genetically determined disorders. There is growing interest in a new discipline of community genetics, which is concerned with equitably delivering the benefits of genetic knowledge to communities and bringing together the experiences of those in primary health care, public health, genetics, and health informatics (1). For example, there is a need for standardized methods for describing the epidemiology of genetic disorders, service audits, and the assessment of their consequences for health.

Haemoglobin disorders are common, can be treated effectively, and can be prevented by screening the population and offering genetic counselling and the option of prenatal diagnosis. These services have been available for over 20 years and they offer the only model of large-scale genetic population screening. The methods developed for service audit have general relevance to population screening (2) and should be incorporated into health services.

Over 5% of the world's population are healthy carriers of a haemoglobin disorder, and couples in which both partners are carriers have a 1 in 4 risk in every pregnancy of having a child with a serious inherited anaemia. Worldwide about 60 000 children with a major thalassaemia and 250 000 with a sickle cell disorder are born annually, giving a rate of more than 2.4 affected children per 1000 births (3). Though originally endemic to the tropics and subtropics, these anaemias are now found worldwide as a result of migration (4).

Carriers can be detected using routine blood tests, and results are, in general, as precise as DNA diagnosis (5). When screening is performed as recommended, over 96% of couples carrying a haemoglobin disorder can be detected and informed of their risk and options before they have children. Community-based "thalassaemia control programmes" -- combining the best possible patient care with prevention through community information, carrier screening, genetic counselling, and an offer of prenatal diagnosis (6) -- have proved highly acceptable in a wide range of cultural settings and have led to a marked fall in the number of children born with this disorder (7-10). The objective of screening is to offer couples who are at risk information and choice.

In the early 1980s, a WHO working group noted that a national register of patients is a powerful tool for obtaining epidemiological information on genetics and for assessing treatment (survival) and prevention (the birth rate of affected children); from time to time patient data has been aggregated in several countries for surveillance purposes. Health services often support the use of registers of congenital anomalies (11, 12), and these occasionally include patients with thalassaemia (13). The only countries where a thalassaemia register (or a register for any other inherited disorder) is explicitly maintained for surveillance purposes are the Islamic Republic of Iran (14) and Oman (15).

Thalassaemia in the United Kingdom

Thalassaemia in the United Kingdom offers a suitable model for demonstrating the surveillance value of a national diagnosis register because treatment and prevention have been available for many years, while the small number of people affected makes it possible to run a national register from a single research centre.

Great Britain is a multi-ethnic society, with 7% of the population and 11% of births in ethnic groups at risk for haemoglobin disorders. It is estimated that more than 0.37 per 1000 fetuses have a major haemoglobin disorder, 80% being sickle cell disorders and 20% being thalassaemias (16). Thalassaemia first appeared as a significant problem in the United Kingdom between 1957 and 1967, when 10% of the population of Cyprus (57 000 people) migrated to London in search of employment and refuge from civil strife (17). …