The NIPT test gives a probability of a baby having Down syndrome. Supposedly, this test is more accurate than the combined test. However, I haven't seen any statistics regarding the accuracy of the NIPT test given the results of the combined test.
Is there an available statistics of the probability for getting a high risk for Down syndrome in the NIPT test, given that the risk in the combined test was low?
Alternatively, is it known that these results are uncorrelated?