stained febrile antigen suspensions can be used to identify and quantitate specific antibodies in human sera following infection with certain Rickettsiae pathogens. These febrile antigens are suitable for both the rapid slide and tube agglutination tests against human sera for the detection of these agglutinins. Rapid Labs stained febrile antigen suspensions can be used to identify and quantitate specific antibodies in human sera following infection with certain Rickettsiae pathogens. These febrile antigens are suitable for both the rapid slide and tube agglutination tests against human sera for the detection of these agglutinins. These antigen suspensions are killed bacteria, stained to enhance the reading of agglutination tests. These antigen suspensions are killed bacteria, stained to enhance the reading of agglutination tests.