ESTRIOL
Estriol was originally added to AFP and HCG to enhance detection of Down syndrome. Estriol concentrations do not influence risk calculations for ONTDs. Researches have shown that Estriol improves Down syndrome detection by only a marginal 1-2%, raising detection from 55% to 57%. Most researchers today agree that Estriol increases the initial positive rate of a screening program without improving the detection rate of Down syndrome or Trisomy 18/13. Consequently we have deleted Estriol to increase detection, to reduce unnecessary positives and cost.
There is a misconception that the use of three markers provides better detection than two markers. On the contrary, the combination of freeBeta and AFP achieves a 21-4% higher Down syndrome detection rate at a lower false positive rate than the “triple test”. In summary, scientific literature has documented the AFP / FreeBeta protocol as the most sensitive and specific.
