These are FeLV/FIV/HW snap tests (Feline Leukemia Virus/Feline Immunodeficiency Virus/Heartworm Antigen) on 3 cats in the same household. The blue dot at the top is the control dot that indicates that the test performed correctly. A dot on the left indicates that the patient is positive for FIV antibody, a dot on the right is positive for leukemia virus, and a dot at the bottom indicates heartworms. The 2 test kits on the right are from known FIV positive cats. The test on the left is from a cat that co-exists peacefully in the same household. He has not contracted FIV (and hopefully never will, since they are all friends and FIV requires a deep bite wound to spread).