New prenatal screening for Down's Syndrome available in the UAE
Mothers-to-be now have an additional option for non-invasive prenatal screening to detect Down's Syndrome and related disorders.
Pregnant women typically go through standard screening during their first two trimesters to help identify chances of chromosomal abnormalities. This includes a series of blood tests and ultrasound scans. The detection rate for Down's Syndrome with these methods ranges from 65 per cent to 96 per cent.
But a non-invasive alternative called "next generation sequencing" is now available in the UAE. It involves drawing 10ml of blood from the mother and analysing the cell-free DNA that is shared between the mother and the foetus. A laboratory will isolate the foetal DNA and count the chromosomes.
Normally, chromosomes come in pairs.
With Down's Syndrome, an extra chromosome is present – a condition known as trisomy.
Although the genetic test can pick up an unusual number of chromosomes, it can only specifically identify abnormalities in chromosomes 21, 18 and 13, which cause Down's Syndrome, Edwards' Syndrome and Patau's Syndrome.
The test is being offered by Trigene through Eastern Biotech and Life Sciences in Dubai, and patients can go directly there or be referred by their doctor.
Women identified to be at high risk have few alternatives other than amniocentesis – an invasive procedure using a needle inserted into the mother's uterus to draw fluid for testing, or Chorionic Villi Aspiration sampling (CVS) – in which a catheter is inserted into the uterus to collect a foetal sample.
In addition to the discomfort, both procedures carry a small risk of miscarriage: amniocentesis at 0.5 to 1 per cent and CVS at up to 2 per cent.
The new technique "is very exciting", said Dr Kulsoom Masood, a gynaecologist at Al Kamal Medical Centre in Sharjah. "For more than 10 years, scientists have been trying to get to the foetal cell-free DNA and they've finally done it. Why subject a patient to pain and discomfort if it is not necessary?"
Cost is the biggest obstacle, Dr Masood said. The screening is not usually covered by insurance and costs about Dh2,000 more than an amniocentesis.
"But I definitely think this will go down as more people demand it," she said.
Dr Amala Nazareth, a gynaecologist at Prime Healthcare Centre in Dubai, has already referred several of her patients.
"It should be recommended to women who are at high risk, those who are over the age of 35, have had abnormal screenings, a past of [foetal] complications or a family history," she said.
The procedure has been clinically validated and is internationally recognised. According to the American Congress of Obstetricians and Gynaecologists (Acog), the technology can be expected to identify about 98 per cent of Down's Syndrome cases with a false-positive rate of less than 0.5 per cent. However, Acog warned that cell-free foetal DNA testing should not be offered to low-risk women or women carrying multiples because it has not been sufficiently evaluated in these groups. It also said that the test should not replace the accuracy of prenatal diagnosis with CVS or amniocentesis.
However, a clinical validation study published in 2010 in the British Medical Journal of 753 pregnant women at high risk of having a child with Down's Syndrome concluded that if referrals for amniocentesis or CVS were based on the new test results, about 98 per cent of the invasive diagnostic procedures could have been avoided.
The test being offered by Eastern Biotech has, so far, no documented cases of false-negatives with a false-positive rate of 0.03 per cent. Another important benefit of the new technology is time, said Dr Sanjida Ahmed, research director at Eastern Biotech.
"Women can be tested as early as 12 weeks and results are provided within two weeks, compared with amniocentesis, which can only be done as early as 16 weeks and another two or three weeks are needed for the results," she said.
"This way mothers can prepare themselves and say: 'OK, I'm going to have a baby with this kind of condition, but now I have an opportunity to learn how to handle it'."
Because of the mixed opinions of the medical community, experts are careful not to suggest the genetic testing for every patient as a replacement for invasive procedures.
"It is a paradigm shift in case of detection but it is hard to convince the doctors and patients at this time," Dr Ahmed said. "We are working hard to change that."
Updated: March 30, 2013 04:00 AM