Which test is commonly used for serologic confirmation of Lyme disease after an initial screening?

Which test is commonly used for serologic confirmation of Lyme disease after an initial screening?

• A. Indirect immunofluorescence
• B. ELISA
• C. Western blot
• D. PCR

Answer: (C)

Lyme disease serology is typically done with a two-tier approach: a sensitive screening test followed by a highly specific confirmation test. The screening step, such as an ELISA, aims to catch most true positives but can yield false positives. To confirm the result and reduce misinterpretation, a Western blot is used next. This test looks for antibodies against multiple Borrelia burgdorferi proteins, and a defined pattern of band reactivity provides much higher specificity than the screening test alone. In practice, if the screen is positive or equivocal, the Western blot is performed to confirm exposure to the organism. PCR, while useful in certain contexts, is not a routine serologic confirmation tool because it detects bacterial DNA rather than antibodies and has limited sensitivity in blood. Indirect immunofluorescence is less standardized and less commonly used as the confirmatory step, making Western blot the appropriate choice for confirmation after screening.

Lyme disease serology is typically done with a two-tier approach: a sensitive screening test followed by a highly specific confirmation test. The screening step, such as an ELISA, aims to catch most true positives but can yield false positives. To confirm the result and reduce misinterpretation, a Western blot is used next. This test looks for antibodies against multiple Borrelia burgdorferi proteins, and a defined pattern of band reactivity provides much higher specificity than the screening test alone. In practice, if the screen is positive or equivocal, the Western blot is performed to confirm exposure to the organism. PCR, while useful in certain contexts, is not a routine serologic confirmation tool because it detects bacterial DNA rather than antibodies and has limited sensitivity in blood. Indirect immunofluorescence is less standardized and less commonly used as the confirmatory step, making Western blot the appropriate choice for confirmation after screening.