Abstract: A method and apparatus are provided for use with a centrifuge to analyze reactants. The apparatus includes at least one cuvette having at least one chamber. The chamber has a radially outward wall which provides a base upon which reactants can be pelleted when the device is rotated about a centrifugal axis. Each cuvette includes one or more openings for introducing fluids to the cuvette and includes a channel positioned adjacent to the radially outward wall for removing fluids from the chamber. Pressure is applied to the chamber to force fluids therefrom, through the channel. A hold down device is also provided through which fluid and/or pressure may be passed with respect to the cuvette. The invention also provides a method for determining the existence and degree of agglutination of reactants in a first fluid suspension and contained in a single reaction vessel using a photodetector.