Lyme Disease Test
There is no single Lyme disease test, which can make diagnosis of this disease difficult in many cases. Several types of Lyme disease test exist, some of which are of dubious accuracy and are not recommended as the basis for diagnosis or treatment. Those tests for Lyme disease which are most widely used are called serologies as they test the blood (serum) of patients for specific antibodies to the Borrelia bacteria that cause Lyme disease infection. Such tests cannot currently differentiate between present active infection and previous exposure to the bacteria and cannot be relied upon for diagnosis in the absence of symptoms of Lyme disease. Where testing occurs shortly after a tick bite it may come back negative as the body requires time to build up detectable levels of antibodies. Serological testing can however be helpful in later stages of Lyme disease.
The two most common Lyme disease test are the Western blot and the enzyme-linked immunosorbent assay (ELISA test). Recommendations from the Centers for Disease Control (CDC) are to perform the ELISA test first, as this is more sensitive, and then follow up with a Western blot if a positive or indeterminate result arises. The specific antibodies tested will depend on the timing of the test after suspected infection and the location of the patient, with US patients and European patients most likely infected with different types of Borrelia bacteria and not, therefore, necessarily creating antibodies of a similar nature. Where a patient has recently travelled to a Lyme endemic area it is important that the tests are also run against region-specific epitopes rather than simply local Borrelia strains. The Western blot is thought to be around 95% accurate for detecting IgM antibodies in early cases of Lyme disease, with the ELISA test about 70% sensitive. In combination, the two tests have a sensitivity of around 64% although this is higher for patients with signs of disseminated Lyme disease such as arthritis in the neck and back or other joints.
Inaccurate Lyme Disease Test
Inaccurate Lyme disease test results do occur, with problems posed by the timing of testing, the specific antibodies being tested, and antibody cross-reactions from other infections that may be present such as cytomegalovirus, herpes simplex, and Epstein-Barr. The rate of false positives in two-tiered testing using Western blot and ELISA is thought to be around 1-3% overall, with false negatives at around 36%. As such, even the standard Lyme disease test cannot be solely relied upon as the basis of a clinical diagnosis. Other tests for Lyme disease exist, including more serological tests such as the Borreliacidal Antibody Assay (Gunderson test), the T-cell activation test, and the indirect fluorescent assay (IFA). Direct detection of Borrelia bacteria can be carried out through polymerase chain reaction (PCR), Lyme Urine Antigen Test (LUAT), skin or tissue culture, and Antigen Capture test although there are significant issues with these types of tests as bacteria are not uniformly present in body tissues or fluids and erroneous results are, therefore, common. Such tests also take considerable expertise and time, making them much more expensive than the ELISA, IFA, and Western blot. The type of Lyme disease test used will depend largely on the resources available to a physician, as well as patient’s symptoms.