What diagnostic test is used as confirmatory after an initial Lyme disease screen?

• A. ELISA
• B. PCR
• C. Culture
• D. Western blot

Answer: (D)

After an initial Lyme disease screen, confirmatory testing uses Western blot because it detects antibodies to specific Borrelia burgdorferi proteins, which adds specificity beyond the screening test and helps confirm a true infection. The screen is designed to be sensitive, but it can yield false positives; the Western blot requires a characteristic pattern of antibody bands, making the result more reliable for confirming Lyme disease. PCR and culture are not used routinely as confirmatory tests after a screening test: PCR has limited sensitivity in blood and culture is slow and often unrewarding. Therefore, the Western blot is the standard confirmatory test.