Abstract: An assay method and kit for a hapten such as theophylline employs a first, latex reagent and a second, antibody reagent. By using a monoclonal antibody of the IgA class in the second reagent, interference by patient rheumatoid factor is prevented.

Abstract: Methods are provided for the detection of proximal convoluted tubule causing diseases or kidney harmful drug monitoring by detecting the presence of shed normal proximal tubule associated antigens in a body fluid such as urine. The preferred embodiment employs an ELISA sandwich format wherein one monoclonal antibody specific for a first epitopic site on said antigen is immobilized on a solid phase and a second antibody, specific for a second epitopic site on said antigen is directly or indirectly labeled.

Abstract: Disclosed is a process for determining the concentration of unbound hormone, e.g., thyroxine, cortisol, or testosterone, in a liquid sample containing hormone and protein capable of binding the hormone. The sample is incubated with antibody specific to the hormone to be detected and a distinguishable analogue of the hormone, both of which are separated from the sample by semipermeable membranes capable of excluding the passage of natural protein and antibody but which allow passage of the hormone and its analogue. Preferably, the antibody and analogue are contained in semipermeable microcapsules. Free hormone in the sample permeates the membranes and competes for sites of attachment to the antibody with the analogue. The antibody and free hormones are then separated. The amount of analogue present either in association with the antibody or in the remainder of the reaction system is indicative of the level of free hormone originally present in the sample.