The diagnosis of Lyme borreliosis (LB) is commonly made by serologic testing with Western blot (WB) analysis serving as an important supplemental assay. Although specific, the interpretation of WBs for diagnosis of LB (i.e., Lyme WBs) is subjective, with considerable variability in results. In addition, the processing, reading, and interpretation of Lyme WBs are laborious and time-consuming procedures. With the need for rapid processing and more objective interpretation of Lyme WBs, we evaluated the performances of two automated interpretive systems, TrinBlot/BLOTrix (Trinity Biotech, Carlsbad, CA) and BeeBlot/ViraScan (Viramed Biotech AG, Munich, Germany), using 518 serum specimens submitted to our laboratory for Lyme WB analysis. (7), confirming that the disease continues to represent a significant public health threat. The clinical manifestations of early localized disease range from nonspecific sequelae, including malaise, myalgia, and lymphadenopathy, to more characteristic findings, such as erythema migrans (EM). In the absence of appropriate therapy, disease progression may lead to significant complications, including rheumatologic, neurologic, or cardiac manifestations (15, 16).The diagnosis of Lyme borreliosis (LB) can be made clinically when patients from regions where the disease is endemic present with EM (5, 8, 18). However, in patients without EM but with objective clinical findings suggestive of disseminated LB, serologic testing is an important diagnostic approach. Appropriate serologic testing should follow the two-tier algorithm recommended by the CDC (6), consisting of initial testing with a sensitive screening assay (e.g., enzyme immunoassay) with positive or equivocal specimens to be tested by Western blot (WB) analysis. Current CDC criteria for WB interpretation recommend that Ն2 bands on the immunoglobulin M (IgM) WB or Ն5 bands on the IgG WB be present for the immunoblot to be considered positive (6, 9). Although WB is considered to be highly specific, current testing protocols in most clinical laboratories rely on visual reading and interpretation of WB strips. These procedures require the laboratory technologist to visually compare band intensities on the patient strip to those of a weakly reactive control. This approach is laborintensive, time-consuming, and subjective, allowing for potential intra-and interlaboratory variation in WB reading and interpretation. Previous studies analyzing the performance of LB serologic tests among testing laboratories have demonstrated significant variation in results, even for more objective methods, such as enzyme immunoassay (2, 3, 10). Therefore, given the inherent subjectivity in reading and interpreting WBs for diagnosis of LB (i.e., Lyme WBs), one would expect to observe significant variation in WB results, with potentially adverse effects on the laboratory diagnosis of Lyme disease and subsequent patient management decisions. Due to the need for more objective and consistent interpretation of Lyme WBs, we undertook a study to evaluate and comp...