The antigens are coated on the nitrocellulose membrane and the sample and enzyme-labeled secondary antibody are added followed by a chromogenic substrate. The substrate is catalyzed by the enzyme labeled on the secondary antibody and the corresponding band on the nitrocellulose membrane is colored, and the result is determined by the presence or absence of the colored band. The technique is simple, rapid, and easy to interpret and can detect a wide range of specific parameters at one time.