A Lyme disease test is administered to detect the presence of Lyme disease in the blood. Lyme disease is caused by bacteria transmitted through the bite of certain kinds of ticks. A test is necessary when symptoms of the disease are exhibited, including inflammation of the skin, an expanding rash, headache, fever and malaise. Because these symptoms are so similar to those of other diseases, diagnosis can be difficult without specialized tests. There are five different types of Lyme disease tests practiced today, including the enzyme-linked immunosorbent assay, or ELISA; the indirect fluorescent assay, or IFA; the polymerase chain reaction test, or PCA; the western blot test; and the skin culture test.
The ELISA or IFA tests are generally administered first, followed by a western blot test. The ELISA and IFA tests are the fastest and most accurate available, and the western blot test is typically used for verification of a positive result. All three tests screen the blood for antibodies which are produced by the immune system to fight Lyme disease. The presence of these antibodies generally indicates an infection.
The PCA and skin culture tests are rarely used, primarily due to their inconvenience. The skin culture Lyme disease test requires that a sample of skin tissue is sent to a laboratory and tested for the presence of the bacteria Borrelia burgdorferi, which causes Lyme disease. However, it takes several weeks to receive the results. The PCA Lyme disease test uses expensive equipment and trained technicians to detect the DNA of the bacteria in the blood stream. However, this method is not yet standardized and can produce false results.
The results of a Lyme disease test are received as two different numbers separated by a colon. The first number of the reading is the concentration of blood used in the test. The second and larger number indicates the amount of salt saline required to fully dilute the blood. Negative test results have a salt saline level of below 256, while positive results are greater than 256. A common positive test result would read 1:312. Western blot tests are used to confirm infections in patients with positive or border-line results.
The results of these tests are not the sole indicator of infection. Several different variables can skew the results, such as high lipid levels, and viral or bacterial infections already present in the bloodstream. Some people don't begin to develop antibodies for as long as 8 weeks after infection, which can result in incorrectly negative Lyme disease test results. Individuals previously infected with Lyme disease may also have false results, as the antibodies will remain in the blood stream for several years after successful treatment.