Streptococcal grouping test. The test method consists of a streptococcal-specific antigen detection by an antibody-antigen reaction. Streptococcal antigens, carried in the streptococcal cell wall, will agglutinate to the corresponding antibody-coated latex particles forming dark blue clumps. This test allows a classification of streptococci into groups A, B, C, D, E, F and G.