Several forms of laboratory testing for Lyme disease are available, some
of which have not been adequately validated. Most recommended tests are
blood tests that measure antibodies made in response to the infection.
These tests may be falsely negative in patients with early disease, but
they are quite reliable for diagnosing later stages of disease.
CDC recommends a two-step
process when testing blood for evidence of Lyme disease.
Both steps can be done using the same blood sample.
1) The first step uses an ELISA or IFA test.
These tests are designed to be very "sensitive," meaning that almost everyone with Lyme disease, and
some people who don't have Lyme disease, will test positive. If the ELISA or IFA is
negative, it is highly unlikely that the person has Lyme disease, and no
further testing is recommended. If the ELISA or IFA is
positive or indeterminate (sometimes called "equivocal"),
a second step should be performed to confirm the results.
The second step uses a Western blot test. Used appropriately, this
test is designed to be "specific," meaning that it will usually be
positive only if a person has been truly infected. If the Western blot
is negative, it
suggests that the first test was a false positive, which can occur for several
reasons. Sometimes two types of Western blot are performed, "IgM" and "IgG." Patients
who are positive by IgM but not IgG should have the test repeated a few weeks
later if they remain ill. If
they are still positive only by IgM and have been ill longer than one month,
this is likely a false positive.
does not recommend testing blood by Western blot
without first testing
it by ELISA or IFA.
Doing so increases the potential for false positive
results. Such results may lead to
patients being treated for Lyme disease when they don't
have it and not getting appropriate treatment for the
true cause of their illness. For detailed recommendations
for test performance and interpretation of serologic
tests for Lyme disease, click
Some laboratories offer Lyme disease testing using assays whose accuracy
and clinical usefulness have not been adequately established. These tests
include urine antigen tests, immunofluorescent staining for cell wall-deficient
forms of Borrelia burgdorferi, and lymphocyte transformation tests.
In general, CDC does not recommend these tests. Click
here for more information.
are encouraged to ask their physicians whether their testing for
Lyme disease was performed using validated methods and whether results were
interpreted using appropriate guidelines.