Even a very low false-positive rate leads to a staggering burden of misdiagnosis. For every reported case of Lyme disease in the United States, approximately 1000 Lyme disease tests are performed annually. But would it be sensitive for the detection of early-stage disease and would it be as specific as Western blot testing for all stages of disease? Specificity is critically important in Lyme disease serologic testing. Ĭould a new Lyme disease serologic test, without the Western blot, perform as well as the conventional CDC 2-tiered algorithm? Could such testing perform better? Without the Western blot, such a test would be easier to perform and standardize. Western blot testing not only results in false-positive IgM testing, but it is costly, has a slow turn-around time, and is subject to intra- and interlaboratory variation. But not all patients demonstrate IgM antibodies as early as 4 weeks, reducing the sensitivity of the test, and not all clinicians follow the 4-week IgM guideline, leading sometimes, among other problems, to the misdiagnosis of late-stage “chronic Lyme disease” on the basis of a false-positive early-stage IgM Western blot. Current CDC guidelines compound the problem by limiting the application of IgM criteria for early diagnosis to the first 4 weeks of illness. This approach works well for the diagnosis of late-stage Lyme disease, as almost all these patients have robust IgG antibody responses to many spirochetal antigens, but not so well in early disease, because the early IgM response may be both insensitive and and nonspecific. Sonicates of whole Borrelia burgdorferi are usually used as the antigen preparation in Western blots. Can serologic testing for Lyme disease be improved? The Centers for Disease Control and Prevention (CDC) currently recommends a 2-tiered algorithm for serodiagnosis, using an enzyme immunoassay or immunofluorescent assay first, followed by immunoglobulin M (IgM) and immunoglobulin G (IgG) Western blots when the first test is positive or equivocal. Indirect, serologic tests will continue to be used to support this diagnosis. It seems unlikely, in routine clinical practice, that direct methods, including culture or polymerase chain reaction, will ever become the primary tests for the laboratory diagnosis of Lyme disease. (See the Major Article by Branda et al on pages 333–40.)
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