Lyme disease: The Daily PANCE Blueprint
A 45-year-old male presents to the clinic with fatigue, migratory joint pain, and a headache that has persisted for two weeks. He recalls hiking in Connecticut four weeks ago and removing a tick from his thigh but did not seek medical attention. One week after the tick bite, he noticed a round, expanding rash on his thigh that resolved spontaneously. Physical examination is unremarkable, and there are no visible skin lesions. What is the most appropriate diagnostic test for confirming Lyme disease in this patient?
A. Blood culture for Borrelia burgdorferi
B. Enzyme-linked immunosorbent assay (ELISA) followed by Western blot
C. Skin biopsy from the rash site with polymerase chain reaction (PCR)
D. Cerebrospinal fluid analysis for Lyme antibodies
E. Direct fluorescent antibody (DFA) testing of the tick
Answer and topic summary
The answer is B. Enzyme-linked immunosorbent assay (ELISA) followed by Western blot
The diagnosis of Lyme disease should be suspected in patients with risk factors for tick exposure and clinical manifestations consistent with Lyme disease. In this case, the patient’s history of tick exposure in an endemic area (Connecticut) and constitutional symptoms align with early disseminated Lyme disease. For patients with early disseminated or late Lyme disease, serologic testing is warranted to support the diagnosis. Two-tiered testing with ELISA followed by Western blot is the standard approach, as it improves specificity and sensitivity, especially after the first few weeks of infection when antibodies are detectable. Although serologic testing alone cannot establish or exclude the diagnosis, it serves as an adjunct to clinical findings.
In contrast, patients presenting with erythema migrans (EM) do not require serologic testing. The diagnosis of EM can be made clinically in patients from endemic areas. Since EM often appears before an antibody response develops, serologic testing may yield false-negative results in early localized disease.
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Covered under ⇒ PANCE Blueprint Infectious Disease ⇒ ⇒
Also covered as part of the Internal Medicine EOR and Family Medicine EOR topic list
