Lyme disease diagnosis is primarily based on clinical symptoms and history of potential exposure to ticks in an endemic area. The characteristic "bull's-eye" rash is often indicative of the infection. However, in some cases, the rash may not be present, making diagnosis more challenging. Blood tests, such as enzyme immunoassays (EIA) and Western blot, can detect antibodies against the Lyme disease bacterium and are used to confirm the diagnosis.