Test procedure Blood is drawn from a vein in your arm, or a sample of CSF is obtained and sent to a laboratory for analysis. For care after drawing of CSF, see Lumbar Puncture, chapter 23. Factors affecting results False-negative results are common three to five weeks after infection, when the antibodies are present in small amounts. Antibody levels tend to rise after the initial infection, peak after six to eight weeks of illness, and decline after four to six months, although in some people they remain elevated indefinitely. False-positive results may be caused by a variety of disorders, including infectious mononucleosis, rheumatoid arthritis, lupus, periodontal disease, and other diseases caused by spirochetes.
Tests performed in various laboratories differ in their reliability.
Identical blood or CSF samples sent to different laboratories may produce different results. When the doctor considers Lyme disease unlikely, negative test results may help rule it out. Advantages It provides the most practical way of confirming the diagnosis of Lyme disease. False-positive results may lead to inappropriate and ineffective treatment. The next step Together with the presence of symptoms and the doctor's observations, a positive test is often sufficient to begin treatment.