The invention provides inexpensive kits and methods for determination of an analyte in a sample with very high sensitivity. Analyte can be determined using an analyte binding member such as an antibody or an oligonucleotide, which can be directly or indirectly linked to an enzyme. The kit and method uses a compound that is altered in the presence of the enzyme, and that precipitates into crystalline particulates. The reaction composition with crystalline particulates is placed between two polarizers which are in an orthogonal arrangement, and the presence of particulates is observed, correlating to the analyte in the sample.