Which statement about Lyme disease serology is true?

Which statement about Lyme disease serology is true?

• A. False positives can occur with syphilis on ELISA
• B. ELISA always confirms infection
• C. Western Blot is never necessary
• D. PCR alone suffices for diagnosis

Answer: (D)

Lyme disease serology depends on a two-step testing approach because no single test perfectly distinguishes active infection from prior exposure. An ELISA screen looks for antibodies against Borrelia burgdorferi, but it can yield false positives due to cross-reactivity with antibodies from other infections, including syphilis. This is why a positive or equivocal ELISA must be followed by a confirmatory Western blot, which requires a specific pattern of Borrelia antibodies and greatly improves specificity. That cross-reactivity with syphilis makes false positives on the ELISA possible, so this statement is true. The ELISA alone does not confirm infection, since confirmation with the Western blot is part of the standard approach. The Western blot is not Never necessary; it is a necessary step after a positive or equivocal ELISA in the typical two-tier testing strategy. PCR by itself is not sufficient to diagnose Lyme disease, as it has limited sensitivity on blood and is not used as the sole diagnostic criterion; when used, it’s more informative on specific specimens like joint fluid or CSF in certain late or neurologic presentations and still interpreted in the clinical context.

Lyme disease serology depends on a two-step testing approach because no single test perfectly distinguishes active infection from prior exposure. An ELISA screen looks for antibodies against Borrelia burgdorferi, but it can yield false positives due to cross-reactivity with antibodies from other infections, including syphilis. This is why a positive or equivocal ELISA must be followed by a confirmatory Western blot, which requires a specific pattern of Borrelia antibodies and greatly improves specificity. That cross-reactivity with syphilis makes false positives on the ELISA possible, so this statement is true.

The ELISA alone does not confirm infection, since confirmation with the Western blot is part of the standard approach. The Western blot is not Never necessary; it is a necessary step after a positive or equivocal ELISA in the typical two-tier testing strategy. PCR by itself is not sufficient to diagnose Lyme disease, as it has limited sensitivity on blood and is not used as the sole diagnostic criterion; when used, it’s more informative on specific specimens like joint fluid or CSF in certain late or neurologic presentations and still interpreted in the clinical context.