EVOLUTION OF AN INHIBIN-A ELISA METHOD - IMPLICATIONS FOR DOWNS-SYNDROME SCREENING

The development of a sensitive and specific enzyme-linked immunoassay (ELISA) for inhibin A stimulated the observation that inhibin A was a useful prenatal marker of Down's syndrome. Modifications of that ELISA , in terms of pre-assay sample treatment, detection methods and standa rd preparation, were subsequently introduced to improve assay performa nce and reduce costs. These modified formats have been validated and r eported. We describe the modifications in detail, explaining the ratio nale for each, and report the results of a study directly comparing th e various ELISA formats in terms of assay performance when applied to clinical samples and ability to differentiate between normal and Down' s syndrome pregnancies. A format involving sample pretreatment with so dium dodecylsulphate at 100 degrees C was found to give better assay p erformance and a modest improvement in discrimination between Down's s yndrome samples and controls, and we recommend this format for use by other investigators.