What are antibody serology tests?

Antibody serology tests look for specific antibodies in your blood. Antibodies are proteins your immune system makes to fight disease-causing germs (also called pathogens), such as viruses and bacteria.

Your immune system creates antibodies after you've been:

• Infected with or exposed to a pathogen.
• Vaccinated against a pathogen.

In both cases, your body stores the antibodies so that they can fight that pathogen if you're ever exposed to it again. A vaccine, however, teaches your body how to make antibodies before you're ever exposed to a pathogen. This way, you don't have to get an infection before developing immunity.

It may take a few weeks for your body to make antibodies after you have had an infection, been exposed to a pathogen, or had a vaccine.

Other names: antibody titer test, antibody test, antibody serum test

What are they used for?

Antibody serology tests are generally used to look for antibodies. However, the type of test used can vary depending on:

• The type of antibody or pathogen the test is being used to detect.
• What condition your provider is attempting to diagnose.
• Whether or not you're receiving medical treatment.

The most common use for an antibody serology test is to look for antibodies to specific diseases. These are called endogenous antibodies, and your body makes them after being exposed to a pathogen or after being vaccinated against it. When testing for endogenous antibodies, your provider can:

• See if you've had a specific infection.
• Check for antibodies that may be a sign of an autoimmune disease (a type of disease that causes your immune system to attack your own cells, tissues, and/or organs by mistake).
• Determine if you need another vaccination (booster shot) for a specific disease.

Antibody serology tests are not used to diagnose diseases such as:

• Measles and mumps.
• Chickenpox and shingles (which are both caused by the varicella-zoster virus).
• Hepatitis.
• Mononucleosis.

They look only at your body's response to a pathogen by checking if you have antibodies to a disease. Because of this, these tests can't show if the antibodies are from a current or past infection or from a vaccination.

A provider may use a different type of antibody serology test when monitoring your response to certain treatments, including those for:

• Cancer.
• Organ transplant rejection.
• Inflammatory and autoimmune disorders.
• Osteoporosis.
• Severe viral infections.
• Nervous system disorders.

These tests check your blood for monoclonal antibodies. Laboratories make monoclonal antibodies to only interact with specific cells, such as those that are cancerous. Because their targets are so specific, these artificial antibodies can make treatment much more effective. They can, for example, bind to a cancerous cell and mark it for attack by your immune system. By checking your monoclonal antibody levels, your provider can see how well your body is handling a certain treatment.

Why do I need an antibody serology test?

You may need this test:

• To find out if you've had a recent or past infection.
• To check your vaccination status. If your medical records are incomplete, you may need this test to find out if you've been vaccinated.
• To find out if a vaccine is effective. If you've already been vaccinated against a disease, the test can show if your vaccine is providing enough protection.
• As a requirement for your school or job. Some organizations may require proof of past infection or vaccination.
• To find out if you have an autoimmune disease, such as lupus.
• If you're receiving any treatment that involves monoclonal antibodies.

What happens during an antibody serology test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for this test?

You don't need any special preparations for an antibody serology test.

Are there any risks to this test?

There is very little risk to having a blood test. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

Your results will depend on which antibodies were measured. Results may be given as titers (levels of antibodies), positive (you have antibodies), or negative (you do not have antibodies).

Common results for antibody serology tests that look for endogenous antibodies include:

• Antibodies to a specific pathogen were found. This may mean you had an infection before. It could also mean you've been vaccinated against a certain disease.
• Low levels of certain antibodies were found. This may mean an earlier vaccination does not provide you with enough protection against a disease. It also means you may need a booster shot.

While antibody serology tests can show that you have an immune response to a pathogen, they cannot show if you have full protection from it or how long that protection lasts.

Results for antibody serology tests that look for monoclonal antibodies depend on the type of treatment you are receiving. Talk to your provider about what these results mean.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an antibody serology test?

An antibody serology test may also detect autoantibodies. Autoantibodies are a type of antibody that attacks healthy cells by mistake. If they're present in your antibody serology test results, your provider may order separate autoantibody tests to determine if you have an autoimmune disease.