The best initial test is?

enzyme linked immunosorbent assay

Enzyme linked immunosorbent assay (ELISA) is the initial screening test for any patient with a recent history of travel or residency in an area endemic for Lyme disease, has a risk of exposure to ticks, and has symptoms consistent with early disseminated or late Lyme disease.

This patient meets all of these criteria for initiating this screening serologic testing.

Lyme disease, caused by Borrelia burgdorferi, is transmitted by the black-legged ixodes tick and is typically found in northeastern United States.

Early localized disease typically includes a bullseye-like rash called erythema migrans and other nonspecific viral-like syndrome symptoms such as fatigue, joint pain and swelling, and fevers.

The knees are common sites of joint pain in Lyme disease.

EARLY disseminated disease manifests with possible neurologic, cardiac, ocular, or other cutaneous findings.

LATE disease includes arthritis, worsening neurologic findings resembling encephalopathy, and further cutaneous features.