Automated method and device for performing solid-phase diagnostic assay

A disposable device suitable for performing automated solid-phase diagnostic assays which employs microparticles to complex an analyte and where the microparticle complex becomes retained and immobilized on a fibrous matrix such that the presence of analyte on the microparticles can be detected by optical means. A device is disclosed having a sample well for receiving a sample and reagents for forming a reaction mixture, a read well comprising (a) an entrance port and holding means for receiving and holding a quantity of sample and assay reagents, (b) a fibrous matrix for retaining and immobilizing microparticle/analyte complexes for detection, said fibrous matrix positioned below said holding means, and having an average spatial separation of fibers greater than the average diameter of said microparticles, (c) means positioned below said fibrous matrix for assisting the flow of sample and assay reagents through said fibrous matrix, such as an absorbent material or vacuum below said fibrous matrix, (d) means for creating a substantially light-tight real surrounding the well, (e) means for venting air entrapped in the absorbent material and which is displaced by fluids absorbed therein, and (f) passage means communicating between the sample well and the read well whereby sample and reaction mixtures can be transferred and washed from said sample well into said read well without being contacted by any apparatus.