Beta-Thalassemia Screening

Screening_BETATHALASSEMIA

Last Updated December 20th, 2021

What is Beta-thalassemia?

Beta-thalassemia is the most common single-gene inherited disease in the world. In fact, this is not one single disease but a group of diseases characterized by reduced production of hemoglobin in the blood that leads to severe anemia.

Hemoglobin is a protein present in the RBC or red blood cell that is responsible for the transport of oxygen within the body. Beta-thalassemia patients will show symptoms of chronic anemia and would require regular blood transfusions.

What does Beta-thalassemia screening mean?

Screening for genetic disorders can help the parents be well-prepared from the beginning of what kind of care would the newborn require if the screening process yields a positive result. Beta-thalassemia screening refers to the process of obtaining a blood sample of the parent (if he/she is a carrier of the disease) and testing it to determine if the fetus has a chance of acquiring the disease.

For pregnant women, who are carriers of beta-thalassemia blood disorder, it is best to undergo the screening procedure before the first 10 weeks of pregnancy. All pregnant women have to undergo screening for thalassemia. In regions where beta-thalassemia is common, all pregnant women are by default required to undergo beta-thalassemia screening.

Is Beta-thalassemia common in India?

The regions where Beta-thalassemia is widely prevalent are the Mediterranean regions, African nations, and South-East Asia. Globally, more than 240 million people have been reported to have this disease. In India, approximately 30 million cases of Beta-thalassemia have been identified.

What are the symptoms shown by an infant with Beta-thalassemia?

The following symptoms are exhibited by a newborn who has inherited Beta-thalassemia:

– Severe anemia which can be only managed via regular blood transfusions during the initial months after birth.

– Frequent infections and bone deformities

– Progressive enlargement of liver and spleen as a result of chelation therapy

Without timely diagnosis and treatment, Beta-thalassemia can cause death within the first two years of life.

What is the price of undergoing a Beta-thalassemia screening in India?

Beta-thalassemia screening or thalassemia profile test in India can cost around Rs. 1500 to Rs 2000 depending upon the city and lab facilities available.

How is Beta-thalassemia actually inherited?

Genetic diseases such as Beta-thalassemia are acquired only when these are passed on from parent(s) to the offspring. This disease gets passed on to the baby if it inherits one defective gene from each parent. This gene dictates how hemoglobin is produced in the body.

There are chances that an individual might just be a carrier of the disease and not actually have the disease. This occurs when only one defective gene is inherited from the parents. In medical terms, this is also referred to as having a trait of the genetic disease. Theoretically speaking, every carrier can pass the defective gene to its offspring.

If both the parents are carriers of the Beta-thalassemia gene, then each time they conceive the fetus has

– 25% chance of not getting the disease at all
– 50% chance of being a carrier
– 25% chance of inheriting the disease.

How is a prenatal screening of Beta-thalassemia done?

The prenatal screening of Beta-thalassemia can be done by the following diagnostic procedures

Chorionic villus sampling (CVS) – This is usually performed during the 11-14th week of pregnancy. In this procedure, a small sample of the placenta tissue is taken and tested for sickle cell anemia or Beta-thalassemia.

Amniocentesis- Beyond 15 weeks of pregnancy, instead of CVS procedure, amniocentesis is performed. Here, a small sample of the amniotic fluid is extracted from the womb. This is tested for the presence of Beta-thalassemia.

What are the steps followed in a Chorionic Villus Sampling or CVS procedure?

This screening test is performed for the early detection of genetic disorders or chromosomal abnormalities in a fetus such as Down’s Syndrome or Edward’s Syndrome. This is not conducted for all pregnant women; it is reserved for those cases where either parent might be a carrier of defective genes.

This includes a previous pregnancy where the fetus was diagnosed with a genetic/chromosomal disorder and/or having a family history of the same. A small part of the placental tissue is removed by either one of these processes:

Transabdominal CVS – a needle is inserted through the womb. This is the most common method used for sample collection.

Transcervical CVS – A tube or small forceps are inserted through the cervix (the neck of the womb) to collect the placental tissue.

The entire process doesn’t take more than 30 minutes. It is a pain-free procedure, though some might find it uncomfortable. Many have reported experiencing period-cramp type pain following the procedure.

How is amniocentesis performed?

Amniocentesis is usually carried out between the 15th to 20th weeks of pregnancy, but you can be performed later also if required. If it is performed before the 15th week, it may increase the risk of side-effects involved with the procedure.

The main complications of an early amniocentesis include – high risk of miscarriage (1 out of 100), infections (1 out of 1000), and the child being born with a club foot.

During the test, a long, thin needle is inserted through your abdominal wall, guided by an ultrasound image. This needle passes into the amniotic sac, a sac that surrounds the fetus and contains amniotic fluid.

The syringe is used to extract the amniotic fluid from this region and the sample is sent to the lab for analysis. The test itself usually takes about 10 minutes, although the whole consultation may take about 30 minutes. Amniocentesis is usually described as being uncomfortable rather than painful.

How is Beta-thalassemia screening performed on newborns?

For newborns, the screening process is generally performed by using the HPLC process (high-performance liquid chromatography), which tests for the presence or absence of hemoglobin in the blood sample.

The blood sample is usually collected from the heel of the newborn and sent to the lab for analysis. Generally, a procedure known as hemoglobin electrophoresis is used to determine and identify different components of hemoglobin present in the infant’s blood sample.

Newborns who don’t have the disease will carry two types of hemoglobin – fetal (Hgb F) and adult (Hgb A). If a newborn has Beta-thalassemia, it will have higher than normal fetal hemoglobin levels and very low (or even zero levels) of adult hemoglobin.

What is the normal reference range for different hemoglobin types used for Beta-thalassemia screening?

The different types of hemoglobin found in a newborn’s blood sample are – Fetal hemoglobin (F), adult hemoglobin (A), and hemoglobin C, D, E, M & S (these are rare and caused by genetic mutations). Hemoglobin F is found in fetuses and newborns and is soon replaced by hemoglobin A. The level of fetal hemoglobin decreases during the first year.

In newborns, 60-70% of hemoglobin F is considered to be normal and as the child approaches 1, it must normally diminish to just 1-2%. In adults, the level of hemoglobin A must lie within the healthy range of 95-98%.

What are the risks and side-effects associated with Beta-thalassemia screening?

Blood tests such as CBC or hemoglobin electrophoresis
– Bruising
– Excess bleeding
– Infection at the puncture site

These are the common side-effects as seen in the case of any blood test. However, in rare cases, the vein may swell after blood is drawn via the syringe. This condition, known as phlebitis, can be treated with a warm compress several times a day.

Chorionic Villus Sampling
– Feeling dizzy and lightheaded
– Abdominal discomfort
– Menstrual cramps-like pain
– Infection
– Rupture in the amniotic sac
– Hemorrhage
– Miscarriage

Amniocentesis
– Fetal or maternal hemorrhage
– Fetal injury
– Miscarriage
– Infections (rare)
Preterm labor (rare)

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