What is the purpose of the Western Blot in Lyme disease serology?

• A. To screen for Lyme disease
• B. To confirm a positive ELISA
• C. To quantify antibody titer
• D. To detect Borrelia burgdorferi DNA by PCR

Answer: (B)

The main idea is that the Western blot in Lyme disease serology is a confirmatory test used after an initial screening test. In practice, you screen with an ELISA to detect possible Borrelia burgdorferi antibodies, and if that result is positive (or equivocal), you use the Western blot to confirm the finding. The Western blot looks for antibodies against multiple Borrelia proteins, providing greater specificity than the ELISA alone. It isn’t used for screening, nor does it quantify antibody levels or measure bacterial DNA—that role belongs to ELISA screening and to PCR, respectively. So the Western blot’s purpose is to confirm a positive ELISA, ensuring the serologic diagnosis is more reliable.