I think that there are two tests. First there is a non invasive test that can be done to evaluate if the foetus is "at risk" of Downs. Then there is a sampling one that is very specific. Basically counting the chromosomes. But the catch is that the specific test carries a risk to the pregnancy - so it's not applied without cause. As well as the sensitivity issue in the article there is also a specificity issue.

My daughter was tested (non invasively) as at high risk of downs (the doctor said 50/50) we decided we didn't care... lo and behold: she doesn't have downs. I don't know enough about the area to make judgements, but I am definitely concerned that it's not a slamdunk that the doctors are getting this right.

There is a huge agenda of control around pregnancy in the UK - our consultant was so arsey about us not doing the follow-up that I had to get him changed out (it later turned out that he was struck off 2 years later for more or less murdering a woman and child, but that's another story).