What is a Western Blot Test?

The western blot test uses a method called gel electrophoresis to separate proteins by molecular weight and length. These are then transferred to a special paper, such as nitrocellulose, that is coated with antibodies. If the antibodies bind to the antigens, a color change occurs on the resulting film. The resulting pattern can indicate the presence or absence of the antibody or antigen. It is used as a diagnostic test for certain infections, including Lyme disease, HIV (Human Immunodeficiency Virus) infection, BSE (Bovine Spongiform Encephalopathy also known as “mad cow disease”), and Hepatitis B Virus (HBV). It is usually performed as a second, more specific test after an initial high sensitivity ELISA or IFA test with positive or equivocal results.

In a HIV Western blot, scientists look for antibodies in a person’s blood that stick to a number of different proteins found on the surface of the virus envelope. In order for a result to be considered positive, it must contain antibodies against at least three of these proteins: gp41, gp120/gp160 and p24. Different algorithms are used to assign positivity.

Western Blot Test: A Critical Tool for Protein Detectio

Indeterminate HIV Western blot tests often result in months of observation, interviewing and testing to determine whether a client has been exposed to or infected with the virus. While these indeterminate tests can be frustrating for both clients and clinicians, they are the best available tools to help determine if a client has been infected with HIV. The goal is to reduce the stress of unreliable test results, which can lead to unnecessary concerns, anxiety and distress for clients.