Lyme Disease Tests
A clear diagnosis of Lyme disease can be difficult, and relies on information the
patient provides and the doctor's clinical judgment, particularly through elimination of
other possible causes of the symptoms. Lyme disease may mimic other conditions, including
chronic fatigue syndrome (CFS), multiple sclerosis (MS), and other diseases with many
symptoms involving multiple body systems. Differential diagnosis (distinguishing Lyme
disease from other diseases) is based on clinical evaluation with laboratory tests used
for clarification, when necessary. A two-test approach is common to confirm the results.
Because of the potential for misleading results (false-positive and false-negative),
laboratory tests alone cannot establish the diagnosis.
Antibody Tests for Lyme Disease
Antibodies are the immune system's response to "fight
off" infection. Tests strive to be both sensitive (detecting any LD antibodies) and
specific (detecting just LD antibodies).
Test Interpretation
- False Negative tests occur due to defects in test sensitivity; too
low an antibody level to detect (e.g. they are bound to the bacteria, with too few
free-floating; the patient taking antibiotics or other drugs; naturally low antibody
production); the bacterium has changed, limiting recognition by the immune system; or
bacterial strain variations.
- False positive tests occur due to test failure or cross-reacting
antibodies (e.g. syphilis, periodontal disease, ANA or RF).
Types of Tests
- Titer (ELISA, EIA, IFA) - These tests measure the level of Bb
antibodies in fluid. Laboratories use different detection criteria, cut-off points, types
of measurements, and reagents.
- Western blot - This test produces bands indicating the immune
system's reactivity to Bb. Laboratories differ in their interpretation and reporting of
these bands.
More specific Lyme Disease Tests
- Antigen detection - These tests detect a unique Bb protein in
fluid (e.g. urine) of patients. This may be useful for detecting LD in patients taking
antibiotics or during symptom flare-up.
- Polymerase chain reaction (PCR) - This test multiplies the number
of Bb DNA to a detectable measurable level.
- Culturing - Growing the bacterium in culture is difficult and can
take months.
- Staining - Staining of tissue is time consuming and has low yield.
The problem is that in Lyme disease there are too few of the Lyme spirochete in the body,
and could result in the biopsy having no bacteria.
|
