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What is Western blot used for?
How accurate is HIV blood test?
Can western blot be false negative?
Jan 21, 2023 · Western blot HIV tests usually look for antibodies against the following HIV proteins: Proteins from the HIV envelope: gp41, and gp120/gp160. Proteins from the core of the virus: p17, p24, p55. Enzymes that HIV uses in the process of infection: p31, p51, p66.
- Overview
- What is the Western blot test?
- What is the Western blot test used for?
- What’s the procedure like?
- How much does the Western blot test cost?
- How accurate are the results, and how long do they take?
- Takeaway
The Western blot test is an antibody test that’s done on a blood sample. It’s used to confirm or disprove the results of an earlier test for HIV or Lyme disease.
Technological advances have produced more accurate tests that give faster results than the Western blot test.
In 2014, the Centers for Disease Control and Prevention (CDC) recommended that the Western blot test for HIV be discontinued in favor of other antibody/antigen tests.
In 2019, the CDC also recommended a different testing protocol for Lyme disease. However, the Western blot test is still often used to test for this condition.
The Western blot test is also known as a protein immunoblot test or immunoblotting. It was invented in 1979 to identify ribosomal RNA binding proteins.
If you get a positive result for Lyme disease or HIV after taking an enzyme-linked immunosorbent assay (ELISA) test, your doctor may recommend a Western blot test to you.
The Western blot test looks for the antibodies against an infection, not the infection itself. If you develop a viral, fungal, or bacterial infection, your healthy immune system will respond to the presence of foreign antigens by producing unique antibodies that bind to the antigen, triggering recruitment of inflammatory cells that fight the infection.
The Western blot uses a procedure called gel electrophoresis to identify and separate proteins by molecular weight and length. The proteins are placed onto blotting paper that’s made from a material such as nitrocellulose.
An enzyme is added to the paper. If it causes a change in color, antibodies to a specific infection have been detected.
Since it can take several weeks or months before antibodies are found in blood, the Western blot test may not always be reliable.
The Western blot test is used to confirm or contest a diagnosis of HIV or Lyme disease after an ELISA antibody test comes back positive or negative. Since the ELISA test sometimes produces false positives, a second test is needed to further the diagnosis.
If you have Lyme disease, the Western blot test may detect antibodies to B. burgdorferi, the bacteria that causes this condition.
The Western blot test is a simple blood test. It doesn’t require fasting, or preparation in any way.
Like all blood tests, you may need to fill out a consent form first.
You may have blood drawn at your doctor’s office that’s sent to a lab, or you may go directly to the lab for testing once the test has been ordered. Based upon your doctor’s protocols and the lab used, you should have your test results in 4 or 5 business days.
Just like all blood tests, there are no serious side effects to expect. You may have a slight amount of bruising at the blood draw site. If you get nervous or are uncomfortable doing blood draws, it may help to bring someone with you.
The Western blot test is covered by most health insurance plans. Talk to your insurance provider to determine what your out-of-pocket cost will be.
If you don’t have insurance, you can expect to pay around $125 for a Western blot test. If you get the test in a doctor’s office, additional charges may also apply.
It may take up to 2 months for your immune system to produce antibodies after being bitten by a tick carrying B. burgdorferi.
It may take up to 3 months before antibodies to HIV are produced after exposure.
Since the Western blot test checks for antibodies, it may give false negatives for both conditions if it’s administered too soon.
In some instances, certain conditions such as lupus may also cause false positives to occur.
The Western blot test is a blood test that’s used as a second-step diagnostic tool. If you test positive for HIV or Lyme disease after taking an ELISA test, your doctor may recommend this test to you.
There are other antibody/antigen diagnostic tests which give more accurate or faster results. For this reason, the CDC stopped recommending the Western blot test several years ago.
- Corey Whelan
A Western blot test is typically used to confirm a positive HIV diagnosis. During the test, a small sample of blood is taken and it is used to detect HIV antibodies, not the HIV virus itself. The Western blot test separates the blood proteins and detects the specific proteins (called HIV antibodies) that indicate an HIV infection.
However, the Western blot is no longer used, and today the ELISA test is followed by an HIV differentiation assay to confirm HIV infection. The provider may also order an HIV genetic...
Oct 7, 2023 · David H. Spach, MD. Reviewer: Brian R. Wood, MD. Table of Contents. Background. HIV Testing and the Care Continuum. HIV diagnostic testing is the crucial first step in the HIV care continuum ( Figure 1 ). [ 1] . Establishing a diagnosis of HIV has important implications for both HIV treatment and prevention.
Jun 12, 2018 · What are the Western blot and ELISA tests for HIV? Explaining the tests. Preparation. Understanding results. Alternative tests. The Western blot and ELISA tests are two blood antibody tests...
A person whose Western blot test results continue to be consistently indeterminate for at least 6 months--in the absence of any known risk factors, clinical symptoms, or other findings--may be considered to be negative for antibodies to HIV-1.
