Abstract: Disclosed are an optical flow particle apparatus and method for conducting a particle light scatter-based immunoassay for simultaneously measuring the presence or amount of one or more analytes in a fluid sample which involves the use of a reagent set for each analyte including first binding molecule-coated monodisperse microspheres and second binding molecule-coated colloidal particles in which at least one of the first or second binding molecules specifically binds a respective one of the analytes. In the case where more than one analytes are detected, each monodisperse microperse microsphere of a particular reagent set has a light scatter signal resolvable from that of microspheres of any other reagent set. Changes determined in the distributions of the measured light scatter signals for individual microspheres of each of the particular reagent sets are indicative of the presence or amount of the respective analyte(s) in the sample.

Abstract: Disclosed is an assay for determining the presence of at least one analyte in a sample, which involves the steps of: (a) mixing the sample and predetermined amounts of first test microparticles having disposed thereon a binding molecule which binds a first analyte, and inert reference microparticles to form a reaction mixture, and to allow for the first binding molecule to bind the first analyte; b) counting the numbers of the non-reacted first test microparticles and the reference microparticles; and (c) comparing the number of non-reacted first test microparticles to the reference microparticles to thereby establish a first test value so that the presence of the first analyte in the sample may be determined. In a preferred embodiment, the first test value is compared to a control value for a non-reactive sample, and a change value is calculated therefrom.

Abstract: A pre-analysis chamber having reduced turbulence is provided for a flow particle analyzer. The chamber has a conical diverging section for decelerating sheath fluid flow to form a laminar profile, followed by a conical converging section for accelerating flow. A sample inlet tube is supported in the chamber near the interface between the diverging and converging sections, and terminates in the laminar, accelerated sheath flow. The sample enters the laminar sheath flow to form a discrete sample stream.

Abstract: A particle agglutination-based, stable kinetic method for simultaneously determining the concentrations of multiple analytes in a single fluid sample with the addition of a single reagent, that entails the use of a novel high resolution sheath flow cell, a novel optical flow particle analyzer (FPA), and unidirectional low angle forward light scattering from multiply-sized or refractive indexed, differently coated particles and their aggregates.

Abstract: A particle agglutination-based, stable kinetic method for simultaneously determining the concentrations of multiple analytes in a single fluid sample with the addition of a single reagent, that entails the use of a novel high resolution sheath flow cell, a novel optical flow particle analyzer (FPA), and unidirectional low angle forward light scattering from multiply-sized or refractive indexed, differently coated particles and their aggregates. Also disclosed are two embodiments of an instrument specifically designed to carry out the method of the invention.