Today, approximately 1.2 million people in the U.S. live with human immunodeficiency virus or HIV. The first case of acquired immunodeficiency syndrome (AIDS) was recognized in the United States in 1981. Since then, over 36 million people have died from this unusual viral infection.
Although modern treatments allow people to live with HIV, around 35,000 new infections are still diagnosed each year. One of the keys to controlling HIV is early detection with tools like the Western blotting test.
What is the Western Blot Test?
The protein immunoblot test or Western blot test uses a blood sample to test for HIV antibodies. This antibody test was once commonly used, but there are more accurate ways to detect HIV nowadays. In 2014, the Centers for Disease Control and Prevention recommended that this test be discontinued and replaced with more advanced testing procedures.
History of the Western Blot Test
In 1975, Edwin Southern devised a novel method for analyzing DNA identity, size, and abundance. It entailed using electrophoresis to separate DNA fragments based on size, then transferring the fragments to a membrane and hybridizing with a radiolabeled DNA probe to identify a specific DNA sequence within a DNA sample. Southern gave the approach his name.
Southern’s choice of name for his test started a trend among scientists. In 1977, Stanford University researchers created the Northern blot test similar to Southern’s work. They named their test the Northern blot as a nod to the earlier testing method.
In 1981, W. Neal Burnette developed a testing method using information established by the Northern blot and followed suit by naming it the Western blot test. Burnette’s Western blotting test can detect single proteins and protein modification. It was routinely used to confirm the presence of the anti-HIV antibody in a blood sample. A positive test indicates the presence of HIV.
How the Western Blot Test Works
The Western blotting test searches for antibodies to an infection rather than the virus itself. In reaction to a viral, fungal, or bacterial infection, your body produces proteins known as antigens. Antigens excite your immune system, causing it to produce antibodies in an attempt to combat the disease.
The Western blot test uses gel electrophoresis to pinpoint and separate proteins using their molecular weight and length as identifying factors. Once separated, the proteins go onto a nitrocellulose blotting paper.
The technicians add an enzyme, and if the specialized paper changes color, they know the antibodies for a specific infection are present. The Western blot test isn’t entirely accurate, though. It can take weeks or even months for the body to create antibodies for some forms of infection, including HIV. If the test is given too early, it may not detect the illness, providing a false negative.
Modern Tools for Diagnosing HIV
Diagnosing HIV is generally a two-step process. It starts with the enzyme-linked immunosorbent assay (ELISA) test. If there is a positive from the ELISA, the patient will get a second, more sensitive test. At one point, that would have been a Western blot, but it is no longer used in the US. Today, they do an HIV differentiation assay to confirm the infection.
The healthcare provider may also order a nucleic acid test (NAT), looking for the actual virus and not the antibody. This test is highly sensitive but expensive. It is usually only available to lose who had a high risk of exposure. An example might be a nurse in the emergency room who gets stuck with a contaminated needle. The NAT can detect the virus as early as ten days after the initial infection.
Doctors may still turn to the Western blot test in some situations, but it is no longer the standard test for HIV.