Antenatal screening for Down's syndrome with the quadruple test.

Second trimester screening for Down's syndrome is widely practised throughout the world. We assessed the performance of antenatal serum screening for Down's syndrome with the quadruple test in 46193 pregnancies from 14 hospitals over 5 years. Women who screened positive (risk > or =1 in 300) were offered diagnostic amniocentesis or chorionic villus sampling. Of 88 observed Down's syndrome pregnancies, 71 (81%) had a positive screening result (81% detection rate, 95% CI 72-89), and of 46105 unaffected pregnancies, 3200 tested positive (7% false-positive rate). These results show that the quadruple test is a better method of screening for Down's syndrome than use of maternal age alone (51% detection rate, 14% false-positive rate) and is more effective than other second trimester screening tests. Therefore, we conclude that the quadruple test should be the test of choice in second trimester screening for Down's syndrome.