A direct dot-enzyme immunoassay to detect human ovulation

This paper describes an original dot-enzyme-linked immunosorbent assay (ELISA) for predicting ovulation in women, based on the detection of the pre-ovulatory estrogen peak in urine. A monoclonal anti-estrogen antibody is used which recognizes not only free estrogens but also some of their urinary metabolites (17-glucuro- and sulfo-conjugates) allowing a direct assay on early morning urines. Antigen is immobilized as a spot on a nitrocellulose membrane which is immersed in urine in the presence of this antibody. A peroxidase-labeled second antibody allows the detection of the first antibody bound to the membrane. Antigen and anti-estrogen antibody concentrations are chosen to obtain a maximal enzymatic coloration of spots corresponding to basal urinary estrogen levels and no coloration corresponding to the pre-ovulatory surge. Six menstrual cycles were studied, comparing dot-ELISA results with patterns of: (1) urinary estrogens measured by RIA either directly or after hydrolysis and extraction, and (2) basal body temperatures. The validity of the pre-ovulatory signal obtained and the requirements for an adaptation of this methodology to a reliable home kit are discussed.