The serologic tests most commonly used to aid in the diagnosis of Lyme disease are the immunofluorescence antibody assay or the more sensitive ELISA. The ELISA is 50% sensitive during the early stages of the disease, and almost all symptomatic patients test seropositive during the later disseminated and persistent phases of the infection. These tests should be used only to support a clinical diagnosis of Lyme disease, not as the primary basis for making diagnostic or treatment decisions. Positive IgG and IgM ELISA results are usually confirmed with Western immunoblot testing. Serologic testing is not as useful even for individuals who are early in the course of Lyme disease because of the low sensitivity. Serologic testing is more helpful in later disease, when the sensitivity and specificity are greater. False-positive results can occur in patients with syphilis, Rocky Mountain spotted fever, yaws, pinta, Borrelia recurrentis infection, and various rheumatologic disorders. PCR has been used to detect B burgdorferi DNA in serum and cerebrospinal fluid. Although patients with Lyme disease may test positive on the FTA-ABS test for syphilis, their VDRL test result should be nonreactive.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.