Screening for trisomy 21 (Down's syndrome )

Natural birth prevalence of Down's syndrome increased with Maternal age;
Under  25- 1 in 1500
At 30- 1 in 1000
At 40- 1 in 100.

Second trimester screening
( between 15 and 22 weeks )

1. Double test
Total hCG or free beta hCG + MSAFP ( Maternal serum alpha fetoprotein) + Maternal age
Detection rate 60%
False positive rate 5%

2. Triple test
Double test + uE3 (unconjugated estriol)
Detection rate 68%
False positive rate 5%

3. Quadruple test
Triple test + inhibin A
Detection rate 76%
False positive rate 5%

First trimester screening
(8-14 weeks)

1. Biochemical
beta hCG + PAPP-A + Maternal age
Detection rate 62%
False positive rate 5%

2. USG + Maternal age
NT (nuchal translucency )
Detection rate 77%
False positive rate 5%

3. BC + USG + Maternal age
Detection rate 90%
False positive rate 5%

Integrated test
( First trimester NT, PAPPA + Second trimester beta hCG, uE3, MSAFP)
Detection rate 95%
False positive rate 5%