A "sandwich" solid-phase enzyme immunoassay for lutropin in urine.

In this "sandwich" technique of enzyme immunoassay for lutropin in urine, a highly purified lutropin-specific anti-gamma-globulin is conjugated with alkaline phosphatase. The conjugate is then extensively purified to remove free enzyme and free antibody molecules. The solid phase consists of anti-lutropin immune globulin coupled to polystyrene tubes or beads. The specific antibody on the solid phase binds the lutropin in the urine sample or in the standard solution, which in turn binds to the specific antibody conjugated to the enzyme. The amount of bound enzyme, which is determined colorimetrically, is thus directly proportional to the amount of lutropin in the sample. We optimized assay conditions and report them here. The sensitivity of the assay is equal to that of radioimmunoassay and almost 10-fold that of the hemagglutination inhibition assay. The test can be used to detect the pre-ovulatory surge of lutropin in women.