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Solomon has misinterpreted the column head "Any Positive Band" in our Table 2 as meaning a cut point in the test indicating a positive result when any 1 band is reactive. Receiver operating characteristic curves are calculated across all possible cut points; hence, the term any refers to all possible cut points (0, 1, 2, or 3... positive bands) among any of the measurable immunoblot bands, as opposed to all potential cut points of 3 specific bands (0, 1,2, or 3 positive bands). The ROC curve area is independent of the chosen cut point and, hence, does not change depending on the number of reactive bands considered to indicate a positive result. We agree that the test improves when the number of bands in the test is less restrictive. The appropriate cut point is that which results in the greatest sensitivity and specificity. Although several statistical programs will easily calculate

Background: A 2-test approach for the serologic diagnosis of Lyme disease has recently been proposed. A positive or equivocal result on a first-stage test (eg, an enzyme immunoassay) is followed by a Western immunoblot test. For a sample to be considered seropositive for Lyme disease, the immunoblot result must be positive. Objectives: To assess the accuracy of IgM immunoblotting for detection of early Lyme disease and to establish interpretative criteria for a commercially available immunoblot assay. Methods: Serum samples from 44 patients with erythema migrans were tested by an IgM immunoblot assay. All patients were culture-positive for Borrelia burgdorferi . Serum samples from 2 different control groups were also tested. Interpretative criteria were developed using receiver operating characteristic curves. Results: The presence of any 2 IgM bands was found to be the optimal criterion for a positive test result, and in patients with illness of less than 7 days' duration, this was significantly more sensitive than the criterion of any 2 of the 3 specific bands defined by the Centers for Disease Control and Prevention/Association of State and Territorial Public Health Laboratory Directors Lyme Disease Workgroup ( P Conclusions: Using a commercially available immunoblot test kit, the presence of any 2 IgM bands is proposed as a positive result. The predictive value of a positive IgM immunoblot result, however, is poor in patients with minimal clinical evidence for Lyme disease. Arch Intern Med. 1996;156:2105-2109