DETERMINATION OF ESTROGEN-RECEPTORS BY ENZYME-IMMUNOASSAY - TECHNICALDIFFERENCES BETWEEN LABORATORIES AND THEIR CONSEQUENCES

When multicentre breast cancer trials are performed, receptor analyses must be comparable both over time and in the participating laboratori es, However, we show for the first time a high variability for the dis tribution of oestradiol receptor (ER) values measured by enzyme immuno assay (EIA) from 1987 to 1991. This variability could be explained by calibration changes in the immunoassay kits. We have also analysed the influence on ER-EIA levels of technical differences between laborator ies apart from the assay itself. Many steps emerged as being critical, i.e. homogenisation buffer, homogenisation procedure and cytosol dilu tion. Finally, we show that addition of 4-monohydroxytamoxifen increas es the apparent ER content measured by ELA in 92% of cytosols. Thus, m any factors must be controlled to ensure high precision with ER-EIA as says. We have to be particularly cautious with the conformational chan ges that could occur during cytosol preparation and that could also pr eexist in the tumour samples. Quality controls of cytosol preparation are essential.