Lyme disease laboratory tests

Overview
Lyme disease is diagnosed based on:
 * Signs and symptoms
 * A history of possible exposure to infected blacklegged ticks

Laboratory blood tests are helpful if used correctly and performed with validated methods. Laboratory tests are not recommended for patients who do not have symptoms typical of Lyme disease. Just as it is important to correctly diagnose Lyme disease when a patient has it, it is important to avoid misdiagnosis and treatment of Lyme disease when the true cause of the illness is something else.

Serology
The serological laboratory tests most widely available and employed are the Western blot and ELISA. A two-tiered protocol is recommended by the CDC: the more sensitive ELISA is performed first, if it is positive or equivocal, the more specific Western blot is run. The reliability of testing in diagnosis remains controversial, however studies show the Western blot IgM has a specificity of 94–96% for patients with clinical symptoms of early Lyme disease.

Erroneous test results have been widely reported in both early and late stages of the disease. These errors can be caused by several factors, including antibody cross-reactions from other infections including Epstein-Barr virus and cytomegalovirus, as well as herpes simplex virus.

Polymerase chain reaction (PCR) tests for Lyme disease have also been developed to detect the genetic material (DNA) of the Lyme disease spirochete. PCR tests are rarely susceptible to false-positive results but can often show false-negative results, and the overall reliability of PCR in this role remains unclear. With the exception of PCR, there is no currently practical means for detection of the presence of the organism, as serologic studies only test for antibodies of Borrelia. High titers of either immunoglobulin G (IgG) or immunoglobulin M (IgM) antibodies to Borrelia antigens indicate disease, but lower titers can be misleading. The IgM antibodies may remain after the initial infection, and IgG antibodies may remain for years.

Western blot, ELISA and PCR can be performed by either blood test via venipuncture or cerebral spinal fluid (CSF) via lumbar puncture. Though lumbar puncture is more definitive of diagnosis, antigen capture in the CSF is much more elusive, reportedly CSF yields positive results in only 10-30% of patients cultured. The diagnosis of neurologic infection by Borrelia should not be excluded solely on the basis of normal routine CSF or negative CSF antibody analyses.

New techniques for clinical evaluation if Borrelia infection are under investigation, including Lymphocyte transformation tests and focus floating microscopy. New research indicates chemokine CXCL13 may also be a possible marker for neuroborreliosis.

Other Types of Laboratory Testing
Some laboratories offer Lyme disease testing using assays whose accuracy and clinical usefulness have not been adequately established. These tests include urine antigen tests, immunofluorescent staining for cell wall-deficient forms of Borrelia burgdorferi, and lymphocyte transformation tests. In general, CDC does not recommend these tests. Click here for more information. Patients are encouraged to ask their physicians whether their testing for Lyme disease was performed using validated methods and whether results were interpreted using appropriate guidelines.

Testing Ticks
Patients who have removed a tick often wonder if they should have it tested. In general, the identification and testing of individual ticks is not useful for deciding if a person should get antibiotics following a tick bite. Nevertheless, some state or local health departments offer tick identification and testing as a community service or for research purposes. Check with your health department; the phone number is usually found in the government pages of the telephone book.

Resources
CDC Lyme Disease Diagnosis and Treatment