Serological Test
A serological test measures antibodies in a blood sample. The amount of antibodies helps healthcare providers determine how strongly your immune system responded to a disease. A provider will withdraw a small amount of blood, which a lab will then test. You should have your results in a few days.
What is a serological test?
A serological (sir-uh-LOJ-i-kuhl) test is a type of laboratory test that usually looks for antibodies in a blood sample. Antibodies are proteins that your immune system makes to fight off invaders, including pathogens (like viruses and bacteria).
Healthcare providers can express serological test results:
- Qualitatively (for example, negative, positive or indeterminate)
- Quantitatively (for example, concentration)
- Semi-quantitatively (for example, titer measures how strong an antibody in your blood is by gradually mixing it with a dilution, like saline, until it stops working)
What diseases does a serological test show?
A serological test can detect and/or measure antibodies for many different types of infections, including:
- Chickenpox.
- Measles.
- Mumps.
- Rubella.
- Tetanus.
- Diphtheria.
- Infectious mono.
- Hepatitis A, hepatitis B and hepatitis C.
- HIV.
- Lyme disease.
- Syphilis.
Serological tests can also diagnose many autoimmune diseases, including:
- Antiphospholipid syndrome.
- Lupus.
- Rheumatoid arthritis.
When is a serological test performed?
A healthcare provider may order a serological test to:
- Learn whether you’ve had a specific infection.
- Determine if you need certain vaccines to protect your body from certain illnesses.
- Prove you received required vaccinations, such as for school or work when a record of prior vaccination is missing.
- Make sure your immune system works as expected after a vaccination.
- Diagnose autoimmune diseases.
How does a serological test work?
A healthcare provider gets your blood sample through a blood test. They’ll withdraw a small amount of blood from a vein, usually in your arm. Then, they’ll send your sample to a lab. The lab then detects the antibodies in your blood.
How do I prepare for this test?
Before a serological test, be sure to let the healthcare provider know about all prescription and over-the-counter (OTC) medications you’re taking, including vitamins and herbal supplements. Certain medications and herbal supplements may increase your risk of bleeding.
It’s also a good idea to let the provider know if you have a fear of needles. They can help you relax so the experience is less intense.
What should I expect during a serological test?
A nurse or phlebotomist will likely perform a serological test. A phlebotomist has special training to draw blood from children and adults. When withdrawing blood from a vein in your arm, they’ll:
- Wrap an elastic band above your elbow to promote blood flow
- Clean the area with an antiseptic to reduce your risk of infection
- Ask you to make a fist or squeeze a stress ball to further promote blood flow
- Insert a thin needle (21 gauge, slightly smaller than the size of a standard earring post) in your vein — you may feel a brief pinch or stinging sensation
- Collect your blood sample into a tube (they may need to collect several samples in separate tubes)
Once they collect enough blood, they’ll remove the needle, place a bandage over the area and remove the elastic band.
In some cases, a provider may only need a tiny amount of blood. They’ll prick one of your fingers with a needle and collect a tiny amount of blood on a special piece of paper. Babies may get a heel stick — providers will prick their heels with a needle to get a blood sample.
What should I expect after?
After collecting a blood sample, a provider will put a bandage on the spot where the needle went in. They may ask you to wait for several minutes before standing up and leaving.
What are the risks of a serological test?
In general, a serological test is a very safe procedure. But some risks may include:
- Feeling dizzy, lightheaded or fainting
- Soreness or pain
- Infection
- Bruising
How often should serological tests be done?
It depends. You may need a serological test to confirm that a vaccine is working. This usually takes place four to six weeks after your vaccine. It’s also a good idea to get a serological test if you suspect you had exposure to an infectious disease.
What does a high serological test indicate?
Normal or abnormal serological test results depend on the antibody a healthcare provider is testing for. A serological test detects the amount of antibodies in your blood. But it can’t detect antibodies that bind to antigens. So, you might have a severe infection but have a low or negative result because more antibodies bind to the antigens than exist freely in your blood.
A high result may indicate a previous infection or that your antibodies weren’t able to bind to antigens. A low result may indicate that your immune system was able to rid your body of an infection.
A healthcare provider will interpret your results and explain them to you.
When should I know the results?
You should get the results of your serological test within a few days.
If the serological results are abnormal, what are the next steps?
If your serological results are abnormal, you may need to take another serological test, additional tests or treatment.
When should I call a healthcare provider?
Call a healthcare provider if you:
- Are interested in getting vaccinated against a specific disease.
- Might need a booster shot.
- May have been exposed to a disease.
- Have symptoms that aren’t improving.
References
- National Library of Medicine (U.S.). Antibody Titer Blood Test (https://medlineplus.gov/ency/article/003333.htm). Last reviewed 4/17/2022. Accessed 12/9/2024.
- Park JH, Cha MJ, Choi H, et al. Relationship Between SARS-CoV-2 Antibody Titer and the Severity of COVID-19 (https://pubmed.ncbi.nlm.nih.gov/35570185/). J Microbiol Immunol Infect. 2022;55(6 Pt 1):1094-1100. Accessed 12/9/2024.
- Testing.com. Antibody Titer Test (https://www.testing.com/tests/antibody-titer-test/). Accessed 12/9/2024.
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