In diagnosing Lyme disease, which testing sequence is used?

• A. ELISA followed by Western Blot
• B. Western Blot followed by ELISA
• C. PCR of blood for Borrelia burgdorferi
• D. Culture of Borrelia burgdorferi

Answer: (A)

Lyme disease is diagnosed using a two-step serologic approach. Start with an antibody screening test to catch most cases, then confirm positive or equivocal results with a second, more specific test. The screening test, an ELISA, is designed to be sensitive so it doesn’t miss true infections. If the ELISA is positive or uncertain, a Western blot is performed to confirm by looking for antibodies to multiple Borrelia burgdorferi proteins, which greatly improves specificity and helps rule out false positives. This combination provides a reliable balance between catching true infections and avoiding misdiagnosis from non-Lyme illnesses.

In early disease, serology can be negative, so treatment may be based on classic signs like erythema migrans when the clinical picture is strong. Direct detection methods such as PCR on blood or culture are not routinely used for diagnosis because they have limited sensitivity or practicality for routine use.