Share on Pinterest
Yoshiyoshi Hirokawa / Getty Images

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.

If you have HIV, the Western blot test may detect proteins from the envelope or core of the virus and enzymes generated by HIV infection.

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.

It can also be stressful or worrisome to wait for test results. Keep in mind that testing is a tool that helps your medical team care for you and provide treatments that can manage your condition.

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.