ABSTRACT
Initially, this test was for a single substance, alphafetoprotein (AFP), which was used to identify pregnancies with an increased risk of neural tube defect (NTD), but, subsequently, other assays were added and the test can now be used for Down’s syndrome, as well as for NTDs. The most commonly used test at the time of writing is the triple test, with assays for AFP, oestriol and bHCG. This test will identify pregnancies where the fetus has a raised risk for NTD or Down’s syndrome. Certain unusual patterns of results may suggest other abnormalities, but the test does not reliably detect these. It should be noted that it is essential that the accurate gestational age is known at the time when the test is carried out; inaccurate dating can lead to false positive or false negative results.
