In an area where Lyme disease is common, the rash may be enough for a physician to make a diagnosis. A flu-like illness along with the rash is common, and the physician will also probably look for muscle and joint tenderness, especially around the knees.
When the rash is absent, Lyme disease may be hard to diagnose because the other symptoms mimic those of many diseases. It is important to consider it, however, because early treatment is much more effective at preventing long-term problems.
Blood Tests For Lyme Disease
Physicians do not usually rely on blood tests alone to confirm or rule out Lyme disease, because these tests are expensive and can be undependable. The most widely performed Lyme disease blood tests are:
Enzyme-linked immunoabsorbent assay (ELISA)
Indirect immunofluorescence assay (IFA)
PreVue burgdorferi antibody detection assay
These tests detect the antibodies that the immune system produces to fight Lyme disease.
However, the antibody tests can sometimes give false-positive results (which indicate disease when the disease in question is not present) or false-negative results (which indicate no disease when disease actually is present).
False-positive results can occur when the test picks up antibodies to other spirochetes, including those that cause syphilis or dental infections.
False-negative results may occur if a recently infected person has not yet produced enough antibodies for the test to detect. Drugs such as steroids may reduce the amount of antibodies in the bloodstream and can cause a false negative as well.
Because of the uncertainty involved in the standard Lyme disease tests, positive results must be followed up with another blood test called the Western blot.
The Western blot creates a graph figure that shows bands of different colors or shading that doctors use to interpret a person's immune response.
The ability of the Western blot to detect Lyme disease antibodies reduces the number of false positives obtained with the ELISA test.
Researchers are working on new tests to detect Lyme disease that promise to be more reliable than the procedures that are currently available.
Other tests that can be used to diagnose Lyme disease, or to determine the extent to which it has affected the body, include:
A spinal tap (lumbar puncture), in which a needle is gently placed into the spine through the back and a small amount of fluid is withdrawn, may be useful for an early diagnosis of Lyme disease in people who are experiencing symptoms involving their nervous system.
Single photo emission computed tomography (SPECT) is an advanced imaging procedure that can reveal patterns in the brain that could indicate whether Lyme disease is affecting the central nervous system.
Nice To Know:
Lyme Disease or Ringworm?
Because of the "bull's-eye" description to describe the Lyme disease rash, the condition commonly called ringworm is sometimes confused with Lyme disease, especially by parents worried about children who play in the grass.
Ringworm is a skin infection caused by the same fungus that causes athlete's foot and jock itch.
It usually leaves a ring-shaped mark that is clearly defined and much smaller than the Lyme disease rash.
It is easily treated by regular application of an anti-fungal ointment for a few weeks.
Unlike Lyme disease, ringworm is spread among people.
Nice To Know:
What Other Conditions Resemble Lyme Disease?
Many other conditions cause a rash or other symptoms similar to those of Lyme disease.
The bites of many insects and spiders can cause a skin reaction.
Scleroderma is a progressive illness that causes arthritis-like symptoms.
Pain, swelling, or stiffness of the joints may be a sign of arthritis that is unrelated to Lyme disease.
In children, rheumatic fever, which can follow strep throat, can cause symptoms similar to Lyme disease.
Other infections can produce a fever, headache, and muscle aches.
Mononucleosis (which often affects teenagers) and viral meningitis (which often affects children) can cause severe fatigue and other Lyme-like symptoms.
Other tick-borne illnesses that can be mistaken for Lyme disease include Rocky Mountain spotted fever (most prevalent in the Mid-Atlantic States) and a new infection transmitted by the Lone Star tick (most prevalent in the southern United States).