Topics: Mutation, Sickle-cell disease, Hemoglobin Pages: 9 (3126 words) Published: January 5, 2012
Review Article
Indian J Med Res 134, October 2011, pp 552-560

Invasive & non-invasive approaches for prenatal diagnosis of haemoglobinopathies: Experiences from India R.B. Colah, A.C. Gorakshakar & A.H. Nadkarni

National Institute of Immunohaematology (ICMR), Mumbai, India

Received October 29, 2010 The thalassaemias and sickle cell disease are the commonest monogenic disorders in India. There are an estimated 7500 - 12,000 babies with β-thalassaemia major born every year in the country. While the overall prevalence of carriers in different States varies from 1.5 to 4 per cent, recent work has shown considerable variations in frequencies even within States. Thus, micromapping would help to determine the true burden of the disease. Although screening in antenatal clinics is being done at many centres, only 15-20 per cent of pregnant women register in antenatal clinics in public hospitals in the first trimester of pregnancy. There are only a handful of centres in major cities in this vast country where prenatal diagnosis is done. There is considerable molecular heterogeneity with 64 mutations identified, of which 6 to 7 common mutations account for 80-90 per cent of mutant alleles. First trimester foetal diagnosis is done by chorionic villus sampling (CVS) and DNA analysis using reverse dot blot hybridization, amplification refractory mutation system (ARMS) and DNA sequencing. Second trimester diagnosis is done by cordocentesis and foetal blood analysis on HPLC at a few centres. Our experience on prenatal diagnosis of haemoglobinopathies in 2221 pregnancies has shown that >90 per cent of couples were referred for prenatal diagnosis of β-thalassaemia after having one or more affected children while about 35 per cent of couples were referred for prenatal diagnosis of sickle cell disorders prospectively. There is a clear need for more data from India on non-invasive approaches for prenatal diagnosis. Key words Haemoglobinopathies - India - invasive and non-invasive approaches - prenatal diagnosis

Introduction The inherited disorders of haemoglobin are the most common monogenic disorders globally. Around 7 per cent of the population worldwide are carriers with more than 3,00,000 severely affected babies born every year1. Prenatal diagnosis is an integral component of a community control programme for haemoglobinopathies. Estimating the disease burden, generating awareness in the population, screening 552

to identify carriers and couples at - risk and genetic counselling are prerequisites for a successful prevention programme. The remarkable success of such programmes in the 1970s in Cyprus, Italy, Greece and the UK led to the development of control programmes in many other countries2-6. The extent of the problem in India β-thalassaemia has been reported in most of the communities that have been screened so far in India. While the overall prevalence varies from 1.5 to 4 per



cent in different States, communities like Sindhis, Punjabis, Lohanas, Kutchi Bhanushalis, Jains and Bohris have a higher prevalence (4-17%)7-12. Different reportshaveestimatedthat7500-12,000β-thalassaemia major babies would be born in India each year12 -14. It has also been shown recently by micromapping at the district level in two States, Maharashtra and Gujarat in westernIndiathattheprevalenceofβ-thalassaemiatrait in different districts within these States is variable (0 9.5%). Based on these estimates there would be around 1000birthsofβ-thalassaemiamajorbabieseachyear in these two States alone15. Thus, such data should be obtained from different States to know the true burden of the disease and for planning and executing control programmes. Haemoglobin S (Hb S) is prevalent in central India and among the tribal belts in western, eastern and southern India, the carrier rates varying from 1-40 per cent16-18. It has been estimated that...
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