This test is usually the first one used to detect infection with HIV. If antibodies to HIV are present (positive), the test is usually repeated to confirm the diagnosis. If ELISA is negative, other tests usually aren't needed. This test has a low chance of having a false result after the first few weeks that a person is infected. This test looks for hepatitis B surface antigens in your blood. The test is used to find out whether you have a recent or long-standing infection from the hepatitis B virus (HBV). HBV has proteins called antigens on its surface that cause your immune system to make antibodies. Hepatitis B surface antigens can be found in your blood within several weeks after the infection starts. They are one of the earliest signs of a hepatitis B infection. A hepatitis C antibody test is used to find out if you are infected with the hepatitis C virus (HCV). When your body is infected with a virus, it makes antibodies to fight the virus. The hepatitis C antibody test looks for antibodies that the body makes in response to the presence of HCV. HCV infects the liver, often causing inflammation and damage. It can lead to cirrhosis, liver failure, and liver cancer. It's more common in developing nations. Syphilis is a sexually transmitted infection (STI) caused by the bacteria Treponema pallidum. The VDRL test or the venereal disease research laboratory test is a procedure to check if the person has syphilis. The bacteria that causes this STI infection by penetrating into the lining of the mouth or genital area. However, the VDRL test doesn't look these bacteria. Your body makes antibodies in response to antigens that are produced by the cells that the bacteria damages. Antibodies are a type of protein produced by your immune system to fight off invaders like bacteria or toxins. The VDRL test checks for these antibodies in your system, which can let your doctors know whether you have syphilis.