Abstract: There is described a method for the chemical modification of antibodies and/or antigens in order to minimise sample interference in immunoassays, an immunoassay method in which chemically modified antibodies and/or antigens are employed, the use of chemically modified antibodies and/or antigens in an immunoassay and a kit for assaying biological specimens which comprises the chemically modified antibodies and/or antigens.

Abstract: Dimeric inhibin concentration can be used in the determination of the risk of a women carrying an unborn child affected by chromosomal abnormalities, e.g. Downs Syndrome. A method for antenatal screening for chromosomal abnormalities is carried out by measuring body fluid taken from a pregnant woman for the level of at least one marker or precursor or metabolite of the marker together with the gestational age of the woman are compared with reference values taken from women carrying fetuses with chromosomal abnormalities and/or women carrying normal fetuses, using dimeric inhibin as a marker. A second marker is the free beta subunit of human chorion gonadotropin. An apparatus for carrying out the method described comprises a computer with a means for comparing the values described.