A health practitioner may diagnose Lyme disease based upon the person's clinical symptoms, such as the presence of an erythema migrans (EM) or "bull's-eye" rash, a history of a tick bite, and/or residence in or a visit to one of the areas of the country where Lyme disease is most commonly found. In cases where history and symptoms are sufficient to diagnose Lyme disease, a laboratory test is not usually ordered.
Lyme disease testing is ordered when someone has signs and symptoms that suggest the person has contracted the disease. The preferred test is a blood test to detect the presence of antibodies to the bacteria. If a person has central nervous system symptoms, such as meningitis, then testing may be performed on cerebrospinal fluid (CSF). The Centers for Disease Control and Prevention (CDC) does not recommend Lyme disease testing for people who do not have any symptoms.
- Borrelia IgM and/or IgG antibodies – may also be positive with infections caused by other bacteria similar to Borrelia, such as the bacteria that cause syphilis
- Borrelia western blot – ordered to confirm positive or indeterminate antibody test results
- In special cases, PCR (polymerase chain reaction) testing may be performed on a sample because it is a more sensitive way of detecting an infection with Borrelia. However, this is not an FDA cleared or approved test method and it is not widely available. The CDC does not currently recommend PCR testing for the diagnosis of Lyme disease.
See the article on Lyme Disease Tests for additional details.