Abstract
The quantitative determination of estrogen and progesterone receptors (PR and ER) in breast tumor cytosol has been routinely performed in clinical laboratories to aid in the selection between hormonal and chemotherapy and also to predict prognosis. However, the small amount of tissue available from the increasingly popular fine‐needle aspiration and core biopsies from breast cancer patients requires more sensitive immunoassays for receptor quantification. We have developed two sensitive immuno‐assays for ER and PR on microplate with the use of recently available anti‐ER and anti‐PR antibodies of higher affinity and a powerful signal magnification agent, namely Amdex. The calibrator was a pooled breast tumor cytosol used as calibrator and calibrated against Abbott kits. The protein concentration of the cytosol and the upper normal cutoffs for our assays were reduced to approximately 0.2 mg/mL and 3 fmol/0.2 mg/mL, respectively. Both assays have sensitivities close to 1 fmol/mL, which are sufficiently sensitive for the receptor quantification in fine‐needle aspiration biopsies and cord biopsies of breast tumor. J. Clin. Lab. Anal. 15:138–143, 2001. © 2001 Wiley‐Liss, Inc.