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Invasive & non-invasive approaches for prenatal diagnosis of haemoglobinopathies: experiences from India
R B Colah1, A C Gorakshakar, A H Nadkarni
1National Institute of Immunohaematology (ICMR), Mumbai, India. colahrb@gmail.com
Insights
India faces a high burden of beta-thalassaemia major and sickle cell disease. Prenatal diagnosis is limited, with most referrals occurring after affected children are born, highlighting a need for better screening and non-invasive methods.
Area of Science:
- Genetics and Genomics
- Hematology
- Public Health
Background:
- Thalassaemias and sickle cell disease are the most common monogenic disorders in India.
- An estimated 7,500-12,000 babies with beta-thalassaemia major are born annually.
- Carrier prevalence varies significantly across and within Indian states, necessitating detailed micromapping.
Purpose of the Study:
- To assess the current landscape of prenatal diagnosis for haemoglobinopathies in India.
- To identify challenges and limitations in existing screening and diagnostic protocols.
- To highlight the need for improved prenatal diagnostic strategies, including non-invasive approaches.
Main Methods:
- Review of existing data on carrier prevalence and disease burden.
- Analysis of current prenatal diagnostic techniques, including chorionic villus sampling (CVS) and cordocentesis.
- Evaluation of molecular diagnostic methods like reverse dot blot hybridization, ARMS, and DNA sequencing.
Main Results:
- Limited first-trimester antenatal clinic registration (15-20%) hinders early screening.
- Prenatal diagnosis facilities are scarce, concentrated in major cities.
- >90% of beta-thalassaemia major referrals were post-diagnosis of an affected child, unlike prospective sickle cell disorder referrals (35%).
- Significant molecular heterogeneity exists, with 6-7 common mutations causing 80-90% of cases.
Conclusions:
- Current prenatal diagnosis strategies in India are largely reactive rather than proactive.
- There is an urgent need to expand screening programs and improve access to prenatal diagnosis, especially in early pregnancy.
- Further research into non-invasive prenatal diagnostic methods is crucial for effective management of haemoglobinopathies in India.
Abstract:
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.
