Mapping the prevalence of sickle cell and beta thalassaemia in England: estimating and validating ethnic-specific rates.

A range of estimates for sickle cell and beta thalassaemia have been derived for the different ethnic groups living in the U.K., reflecting uncertainty over the true population value in certain countries and the heterogeneity within and between countries of origin comprising the same ethnic group. These were validated against six community screening programmes, with the estimated range correctly predicting the number of affected births observed by the programmes. In England approximately 3000 affected babies (0.47%) carry sickle cell trait and 2800 (0.44%) carry beta thalassaemia trait annually: with approximately 178 (0.28 per 1000 conceptions) affected by sickle cell disease (SCD) and 43 (0.07 per 1000) by beta thalassaemia major/intermedia. Allowing for termination, about 140-175 (0.22-0.28 per 1000) affected infants are born annually with SCD and from 10 to 25 (0.02-0.04 per 1000) with beta thalassaemia major/intermedia. These are the first evidence-based rates for sickle cell and beta thalassaemia for use in the U.K., and should underpin the future planning of services. The long-term solution to monitoring changes in the rates of trait and disease in the population is to introduce a standardized instrument for collecting ethnicity for all community screening programmes.

Audit of prenatal diagnosis for haemoglobin disorders in the United Kingdom: the first 20 years.

OBJECTIVES: To audit services for prenatal diagnosis for haemoglobin disorders in the United Kingdom. DESIGN: Comparison of the annual number of cases recorded in a United Kingdom register of prenatal diagnoses for haemoglobin disorders, with the annual number of pregnancies at risk of these disorders, by ethnic group and regional health authority. The number of pregnancies at risk was estimated using data on ethnic group from the 1991 census and data from the United Kingdom thalassaemia register, which records the number of babies born with thalassaemia. SETTING: The three national prenatal diagnosis centres for haemoglobin disorders. SUBJECTS: 2068 cases of prenatal diagnosis for haemoglobin disorders in the United Kingdom from 1974 to 1994. MAIN OUTCOME MEASURES: Utilisation of prenatal diagnosis by risk, ethnic group, and regional health authority. Proportion of referrals in the first trimester and before the birth of any affected child. RESULTS: National utilisation of prenatal diagnosis for haemoglobin disorders was around 20%. During the past 10 years it has remained steady at about 50% for thalassaemias and risen from 7% to 13% for sickle cell disorders. Utilisation for sickle cell disorders varies regionally from 2% to 20%. Utilisation for thalassaemias varies by ethnic group. It is almost 90% for Cypriots and ranges regionally for British Pakistanis from 0% to over 60%. About 60% of first prenatal diagnoses are done for couples without an affected child. Less than 50% of first referrals are in the first trimester. CONCLUSIONS: National utilisation of prenatal diagnosis for haemoglobin disorders is far lower than expected, and there are wide regional variations. A high proportion of referrals are still in the second trimester and after the birth of an affected child. The findings point to serious shortcomings in present antenatal screening practice and in local screening policies and to inadequate counselling resources, especially for British Pakistanis.

Neonatal Screening for Haemoglobinopathies in South East London: findings and comparisons with Jamaica

INTRODUCTION: Neonatal screening for sickle cell disorders has been shown to reduce mortality and morbidity. Methods of screening vary but in 1994, the local Health Authority funded universal neonatal screening across the whole of Lambeth, Southwark and Lewisham. This paper will report the findings of the first three years of operation of the programme and compare findings with the screening programme currently operating in Jamaica. METHOD: since May 1994 dried bloo[d] spots of all infants have been screened at King's College Hospital and screen positive cases followed up by counsellors. Infants are followed up at four sites (Guy's, King's, Lewisham and St.Thomas') according to parental preference. Minimum standards for follow-ups have been agreed by clinicians across all four sites and information of the success in achieving these standards is now being collected. RESULTS: Overall there have been 122 affected infants detected in the first two years 10 months of the programmes operation. This is made up of 83 HbSS, 35 HbSC, 4HbSBThal. This gives a birth preference of 23.4 per 1000 total population (2.3HbSS, 1.0 HbSC). Allowing for a termination rate of 20 percent this indicates that the expected birth prevalence in the district would be 4.2 per 1000 births. This compares with birth prevalence of of 0.3 per 1000 for congenital hypothyroidism, 06. per 1000 for cystic fibrosis and 0.1 for phenylketonuria. The distribution of the births is unevem with 57 in Southwark, 40 in Lambeth and 25 in Lewisham. The paper will report on the follow-up and outcome of care provided for this population to date. Discussion: South East London has the highest prevalence of sickle cell disorders of any district in the UK. Sickle cell disorder is now as common in South East London as it is in Jamaica. The follow-up arrangements established in South East London provide an opportunity for colloboration with the West Indies which may help to determine some of the reasons for differences in the natural course of the disease in these populations. The population based approach established should allow monitoring of the impact of community education and antenatal screening programmes on the birth prevalence over time. (AU)