Estrogen receptors by immunofluorescence: comparison with a dextran coated charcoal technique

Biopsy specimens from 21 women with primary operable breast cancer were analyzed in a double blind study designed to compare fluorescent antibody methods for detection of estrogen receptors with estrogen receptors measured biochemically with a previously reported dextran coated charcoal technique (DCC). Fluorescent antibody methoids employed both direct techniques: (1) rabbit antisera to 6-O-Carboxymethyl-Oxime-17 beta Estradiol tagged with Fluorescin Istthiocyanate (FITC) and (2) indirect techniques (sheep antisera to 11-Hemisuccinate-17 beta Estradiol reacted wih FITC tagged rabbit antisheep sera). Fluorescent antibody methods showed 100 percent correlation with each other but only 67 percent correlation with the DCC assay. Fluorescence was striking when present. Molecular forms were not easily predicted. Divergent results occurred largely in specimes sparsely populated with malignant cells (18 percent) though neoplasms showing no fluorescence demonstrated elevated receptor conconcentrations with DCC (15 percent). Indirect fluorescent techniques are the simplest of those studied. Fluorescent techniques have not replaced biochemical techniques in the authors' laboratories.