Is an ELISA Test?
An enzyme-linked immunosorbent assay, also called ELISA or
EIA, is a test that detects and measures antibodies in your blood. This test
can be used to determine if you have antibodies related to certain infectious
conditions. Antibodies are proteins that your body produces in response to
harmful substances called antigens. An ELISA test may be used to diagnose:
- HIV, which causes AIDS
- Lyme disease
- pernicious anemia
- Rocky Mountain spotted fever (RMSF)
- squamous cell carcinoma
- varicella-zoster virus, which causes chicken pox
ELISA is often used as a screening tool before more in-depth
tests are ordered. A doctor may suggest this test if you’re having signs or symptoms
of the conditions above or your doctor wants to rule out any of these
the Test Is Performed
The ELISA test is simple and straightforward. You’ll probably
need to sign a consent form, and your doctor should explain the reason for
doing the test.
The ELISA test involves taking a sample of your blood.
First, a healthcare provider will cleanse your arm with an antiseptic. Then, a tourniquet,
or band, will be applied around your arm to create pressure and cause your
veins to swell with blood. Next, a needle will be placed in one of your veins to
draw a small sample of blood. When enough blood has been collected, the needle
will be removed and a small bandage will be placed on your arm where the needle
was. You'll be asked to elevate your arm and place pressure on it with a gauze to
reduce blood flow.
This procedure should be relatively painless, but your arm
may throb a little after the procedure.
The blood sample will be sent to a laboratory for analysis.
In the lab, a technician adds the sample to a petri dish containing the
specific antigen related to the condition for which you are being tested. If
your blood contains antibodies to the antigen, the two will bind together. The
technician will check this by adding an enzyme to the petri dish and observing
how your blood and the antigen react. You may have the condition if the contents
of the dish change color. How much change the enzyme causes allows the
technician to determine the presence and amount of antibody.
for the Test
There’s no special preparation for this test. The blood draw
lasts only a few moments and is mildly uncomfortable. Tell your healthcare
provider if you have a fear of needles or become lightheaded or faint at the
sight of blood or needles.
There Any Risks?
There are very few risks associated with this test. These
- feeling faint
- bleeding more than usual
Make sure to tell your doctor before the test if you’ve had
trouble giving blood in the past, bruise easily, or suffer from a bleeding
disorder such as hemophilia.
Do the Results Mean?
How the test results are reported varies based on the
laboratory that conducts the analysis. It also depends on the condition for
which you’re being tested. Your doctor should discuss your results and what
they mean. Sometimes, a positive result will mean that you don’t have the
False positives and false negatives can occur. A
false-positive result indicates you have a condition when you actually don’t. A
false-negative result indicates you don’t have a condition when you actually do.
Because of this, you may be asked to repeat the ELISA again in a few weeks or
your doctor may order more sensitive tests to confirm or refute that you have
Else Do I Need to Know?
Although the test itself is relatively simple, waiting for
the results or being screened for conditions such as HIV can cause a lot of
anxiety. It’s important to remember that no one can force you to take the test.
It’s voluntary. Make sure that you understand the laws in your state or the
policy of the healthcare facility for reporting positive HIV results.
Discuss the test with your provider. Remember that
diagnosing any possible infectious disease is the first step toward getting
treatment and protecting others from the infection.