If a patient with an indeterminate test has engaged in high risk behavior, another test should be conducted in six months. There are many bands in a strong positive test because, technically, any proteins that are foreign to the body are antigens. These proteins do not necessarily have to be on the outside of the virus. As a result, there are actually several types of HIV antibodies, each targeting a different HIV protein. The more advanced an infection, the more types of HIV antibodies exist and the more bands that appear.
Some bands are darker than others because some proteins are more abundant in the virus.
Not at all. The problem is that some proteins found in HIV are similar to proteins found in other infectious agents. As a result, just because something in the serum binds to a protein from HIV does not necessarily mean that HIV is present. In combination, the two tests make a good team.