The HIV4 test, also known as the HIV antigen and antibody test, has a window period of about 2-3 weeks. HIV antigens and antibodies can be detected in the blood of a healthy person about 2-3 weeks after he/she is infected with HIV. However, if only the HIV antigen and antibodies are positive, it is not enough to confirm the diagnosis. In China, the diagnosis of AIDS needs to be confirmed by a confirmatory test, which is conducted at the CDC. If the 4-generation test is positive, a protein blot test at the CDC is required to detect the antibodies in the patient’s body. If the protein blot test also detects antibodies to HIV in the patient’s body, the diagnosis of HIV infection is confirmed. Conversely, if the protein blot test does not detect HIV antibodies in the patient’s body, the patient is not infected with HIV.