India’s high genetic disease burdenOctober 10, 2018
In August this year, India’s health ministry proposed mandatory genetic screening of all pregnant women for thalassemia and sickle cell anaemia. Thalassemia is a significant health challenge in India with about 10,000 to 15,000 babies with β-thalassemia major born each year. One of the key points of the draft policy is government’s effort to reduce the birth of affected children through carrier screening and prenatal diagnosis.
If implemented, it will be the first instance of genetic testing becoming widely used in India and could open the floodgates for similar tests. The potential is immense. For instance, there are almost 3.6 to 3.9 crore carriers of β-thalassemia in India, and for sickle cell disease there are about 25,00,000 carriers of the gene (Hemoglobin AS) and about 1, 25,000 patients of sickle cell disease.
In addition, India is reported to have one of the highest incidence of genetic disorders and birth defects. It is estimated that birth defect pervasiveness is 64.4 over 1,000 live births in the country, with 1 out of every 20 newborns admitted to the hospital carrying a genetic disease that eventually accounts for nearly 1 out of 10 infant mortality, indicating that India has a significant burden of neonates with genetic disorders. Globally, the prevalence of genetic conditions varies depending on the use of preventive strategies, access to prenatal screening, diagnosis and the option to terminate a pregnancy in case of severe birth defects.
Genetic testing is a relatively new science that involves the analysis of genes or genetic components, such as the DNA, RNA, chromosomes, proteins and certain metabolites, of the human body to detect variations that could cause disorders or inheritable disease.
“Genetic testing is used quite extensively these days. It has applications in every field of medicine as many diseases have a genetic component,” said Dr. I. C. Verma, senior consultant, Institute of Medical Genetics and Genomics, Sir Ganga Ram Hospital, New Delhi.
There are different kinds of genetic testing including newborn screening, in which neonates are tested for treatable genetic disorders; diagnostic testing, which is used to identify a specific monogenic genetic disorder, such as, Down syndrome or Trisomy 18.
Genetic testing is also used for carrier testing, which is used to identify people who carry one copy of a mutation that, when present in two copies, can cause a genetic disorder, such as thalassemia and sickle cell disease, and predictive testing that is used to detect genetic mutations associated with disorders that appear later in life. These tests can identify mutations that increase a person’s risk of developing disorders with a genetic basis, such as certain types of cancer.
In the West, genetic testing has mushroomed into an industry with centres offering at home diagnostic kits that can create a risk profile for disease ranging from cancer to cardiac disease and almost everything in between.
This could potentially help patients pre-empt the disease. “Once you identify genetic disposition, it is possible to create tailor made treatments for these diseases,” Dr Verma said.
In India, too, there is a growing awareness about genetic testing. An internet search leads to numerous outfits within India that offer to mail kits that one can send saliva samples to and get a detailed genetic profile.
“More and more people are going in for genetic testing and facilities are widely available in bigger cities,” said Dr Jayesh Sheth, chairman of Ahmedabad based Institute of Human Genetics. “However, there should not be indiscriminate use of genetic testing. Instead, it is advisable to go for a tiered approach – the first test should ideally be a karyotype test, then array complete genetic hybridisation and lastly exom studies,” Dr Sheth said. This could ensure that the cost burden to the patient is minimised.
Dr Sheth also recommended the setting up of regional and nodal centres for genetic testing. These should ideally be set up in government hospitals so that the reach of genetic tests is greater and that the cost is also reduced. Currently, though there are many centres for such tests, their distribution is largely in the urban setting and the semi-urban and rural areas have limited or no access. In the event of the government making pre-natal testing mandatory, the implementation of the same could prove to be a logistical nightmare.
Dr Divya Agarwal, a New Delhi based geneticist, stated that in a country like ours, it may not be economically possible.
In addition, doctors feel that the government could do well by recommending simpler screening tests rather than genetic testing. “Carrier screening for beta thalassemia could be done by haemoglobin electrophoresis ,” said Dr Sheth. And they also advocated focusing on other preventive measures to minimise birth defects, such as encouraging fortification of food with essential vitamins like folic acid, which has been found to reduce the incidence of spina bifida.