Scientists at the UK’s Queen Mary University of London (QMUL) have demonstrated a new-method, antenatal reflex DNA screening, for three serious chromosome disorders.
The accurate, safe and less stressful method incorporates DNA analysis into the standard antenatal screening to detect Down’s, Edwards and Patau syndromes.
Reflex DNA screening is reported to have detected more affected pregnancies with less false-positive, compared to the test it replaced.
Existing tests for the disorders require an ultrasound and blood test at 10-14 weeks of pregnancy, followed by invasive diagnostic tests such as amniocentesis or chorionic villus sampling (CVS) in women found to be at an increased risk.
Performed at 11 weeks of pregnancy, the new method only requires a blood sample that is divided into two, of which one undergoes the conventional screening and the other is held in reserve.
If the first test reveals a one in 800 or higher risk of an affected pregnancy, the second sample is automatically retrieved for a reflex DNA test.
Implemented at five NHS maternity units in the country, the method was used to screen more than 22,000 women between April 2015 and August 2016.
Of the total women, 11% (106) had a DNA test, which detected 101 pregnancies affected with one of the three syndromes with four false-positives, indicating 95% detection and 0.02% false-positive rates.
Out of the 26 women who tested positive and were offered an invasive diagnostic test, 25 were reported to be affected by one of the disorders.
QMUL Wolfson Institute of Preventive Medicine professor Nicholas Wald said: “The reflex DNA approach has substantial benefits to the wellbeing of the women screened.
“Reflex screening is also safer than conventional screening as it avoids nearly all invasive diagnostic tests in unaffected pregnancies and miscarriages related to these procedures.”