The present invention is directed immunoassay cuvettes that comprise diffusely bound and non-diffusely bound reagents for carrying out an immunoassay. The reaction and detection are carried out in the immunoassay cuvette. The immunoassay cuvette comprises a transparent front wall, a back wall, side walls, a bottom, and a top opening. The back wall of the cuvette has a substantially planar surface made of a non-porous material and comprises a capture zone having reagents non-diffusedly bound and a signal reagent zone having reagents diffusedly bound.