Editorial Commentary:Laboratory Testing for Lyme Disease: Time for a Change?

Laboratory testing for Lyme disease by the measurement of antibodies to Borrelia antigens using ELISA and Western immunoblot in a 2-tier fashion remains essential to diagnosing this disease [1, 2]. However, this diagnostic methodology is not always necessary, sufficient, properly used, or properly interpreted. An erythema migrans (EM) rash is recognized in 80% of patients with early Lyme disease [3]. As Steere et al. [4] have confirmed in the prospective clinical-laboratory study reported in this issue of Clinical Infectious Diseases, the frequency of a test result positive for Lyme disease remains very low among patients withEM alone (17%), although it increases to ∼50% in the convalescent phase, after antibiotic therapy. However, this anemic diagnostic sensitivity for patients with early Lyme disease who have isolated EM is less important than the sensitivity of the test for patients with other clinical features associated with Lyme disease, because the presence or history of an expanding EM rash is ofter sufficiently characteristic to make laboratory testing unnecessary for therapeutic decision-making [5]. On the other hand, patients with prolonged exposure to Borrelia burgdorferi who exhibit extracutaneous clinical features have positive IgG immunoblot results, which have high specificity and a strong positive predictive value for Lyme disease [6, 7]. However, even a positive immunoblot result is insufficient to diagnose current infection in the absence of current symptoms that are consistent with active Lyme disease, because test positivity may reflect prior infection due to Borrelia species or asymptomatic seroconversion [8–10]. In the study by Steere et al. [4], 11 (79%) of 14 patients with prior Lyme disease had a positive result on 2-tier testing.