Crypto-Giardia Ag Rapid Test (RAP-5403 and 5404) chromatographic immunoassay is a procedure for qualitative measurement of Giardia antigens in stool samples. The test is based on the immunological capture of colored microparticles as they pass through a membrane on which the monoclonal antibody has been immobilized.Crypto-Giardia Ag Rapid Test (RAP-5403 and 5404) use monoclonal Cryptosporidium parvum- and Giardia lambliaspecific antibodies that detect all forms of the parasites' life cycle.The tests are based on the use of three microspheres: blue microspheres which are covalently linked to a monoclonal antiCryptosporidium parvum antibody, red microspheres which are covalently linked to a monoclonal anti-Giardia lamblia antibody, and green microspheres which are used as test control. The parasites present in stool samples react with the latex particles which are coated with monoclonal antibodies specific against the antigen. This latex particles/antibodies/parasite complex migrates through a chromatographic process towards the reaction area. In this area, there are anti-Cryptosporidium and anti-Giardia antibodies, which react with the latex particles/antibodies/parasite complex. This reaction leads to the appearance of a blue line in the case of Crypto and a red line in the case of Giardia. These lines are used to interpret the result, at ten minutes' room-temperature incubation.