Thalassaemia and Sickle Cell: Why Carrier Testing Before Marriage Matters
India has one of the largest burdens of inherited haemoglobin disorders in the world. Both thalassaemia and sickle cell disease are entirely preventable at the population level through carrier screening, and both are frequently diagnosed only after an affected child is born.
Trait versus disease
Everyone has two copies of the relevant gene, one from each parent.
Carrier, or trait, means one abnormal copy. Carriers are generally healthy, have normal lifespans and need no treatment. Many are told they are anaemic and given iron for years, which does nothing and can cause iron overload.
Disease means two abnormal copies, one from each parent.
If both parents are carriers, each pregnancy carries a 25 percent chance of an affected child, a 50 percent chance of a carrier, and a 25 percent chance of a completely unaffected child. The odds reset with every pregnancy; having one healthy child says nothing about the next.
Beta thalassaemia
Reduced or absent production of beta globin chains.
Thalassaemia major presents between 6 and 24 months with severe anaemia, poor feeding, failure to thrive, pallor, an enlarged abdomen from liver and spleen enlargement, jaundice and characteristic facial bone changes. It requires lifelong blood transfusion every two to four weeks plus iron chelation, because repeated transfusion causes iron overload that damages the heart, liver and endocrine glands. Bone marrow transplantation is the only cure and is best done young with a matched sibling donor.
Thalassaemia intermedia is milder, with variable transfusion need.
Thalassaemia minor, the trait, causes mild anaemia with small red cells and no symptoms.
Carrier frequency in India is around 3 to 4 percent overall, higher in several communities including Sindhis, Punjabis, Gujaratis, Bengalis and some others.
Sickle cell disease
A single amino acid change makes haemoglobin polymerise when deoxygenated, deforming red cells into a rigid sickle shape that blocks small vessels and breaks down early.
Features:
- Vaso-occlusive crises: sudden severe pain in bones, chest, abdomen or back, triggered by dehydration, infection, cold, altitude or stress
- Chronic haemolytic anaemia and jaundice
- Dactylitis, painful swelling of hands and feet, often the first sign in infants
- Acute chest syndrome, a medical emergency with chest pain, fever and breathlessness
- Stroke, including in children
- Splenic sequestration, a rapidly fatal emergency in young children where the spleen traps blood
- Increased infection risk from loss of spleen function
- Leg ulcers, priapism, kidney damage, retinopathy, avascular necrosis of the hip
- Gallstones
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Sickle cell trait is usually asymptomatic. Rare complications occur under extreme conditions such as high altitude, severe dehydration or extreme exertion.
Sickle cell disease is concentrated in central and eastern India and among several tribal populations, where carrier rates in some communities exceed 20 percent.
Testing
Complete blood count showing small red cells with a low MCV and MCH.
HbA2 level on haemoglobin electrophoresis or HPLC: raised above about 3.5 percent indicates beta thalassaemia trait.
Solubility test for sickling, confirmed by electrophoresis or HPLC, which distinguishes trait from disease.
Crucial point: iron deficiency can mask thalassaemia trait by lowering HbA2. Check and correct ferritin, then retest if there is doubt.
Genetic testing identifies the exact mutation, which is useful for prenatal diagnosis.
Newborn screening programmes for sickle cell exist in several Indian states, and the national programme aims to eliminate sickle cell disease.
Who should be tested
- Anyone before marriage, particularly in high-prevalence communities
- Both partners when planning pregnancy
- Early in pregnancy, ideally in the first trimester, if not tested earlier
- Anyone with mild persistent anaemia that does not respond to iron
- Siblings and relatives of anyone found to be a carrier
- Anyone with a family history
- Blood donors
Carrier screening is inexpensive, takes one blood sample, and is the single intervention that prevents the disease.
For couples who are both carriers
Options, which should be discussed with a genetic counsellor rather than decided on hearsay:
- Prenatal diagnosis by chorionic villus sampling at 10 to 13 weeks or amniocentesis at 15 to 18 weeks, with informed decisions thereafter
- Preimplantation genetic diagnosis with IVF, selecting unaffected embryos, which can also produce an HLA-matched sibling as a potential marrow donor
- Proceeding with a pregnancy with full knowledge and early treatment planning
- Other family-building options
Being a carrier is not a reason for shame, exclusion from marriage or social stigma, and framing it that way is what drives people away from testing. It is a piece of information that lets a couple make a choice.
Living with the disease
Thalassaemia major: regular transfusion to maintain haemoglobin, iron chelation taken consistently, cardiac and liver iron monitoring by MRI, endocrine monitoring, hepatitis B vaccination, calcium and vitamin D, and consideration of transplant. Never give iron supplements unless a doctor has specifically confirmed iron deficiency.
Sickle cell disease: hydroxyurea, which reduces crises substantially and is under-prescribed; penicillin prophylaxis and full vaccination in children; folic acid; generous hydration; avoiding cold, dehydration and extreme exertion; prompt treatment of fever as an emergency; transcranial Doppler screening in children to prevent stroke; and newer agents and transplant in selected cases.
For both: pain must be taken seriously and treated adequately. Under-treatment of sickle cell pain, often from suspicion about opioid-seeking, is a well-documented failure of care.
This is general information. Carrier testing, genetic counselling and treatment decisions should be made with a haematologist and a genetic counsellor.