) have shown that patients infected with B. burgdorferi
produce high concentrations of highly specific borreliacidal antibodies. Researchers (9
) have also demonstrated that borreliacidal antibodies can be accurately detected in well-characterized culture- or case-defined Lyme disease sera by using a flow-cytometric BAT. In this study, we determined how the BAT would perform in a primary-care practice located in a region where Lyme disease is common (2
Using sera from patients with early Lyme disease characterized by a classic EM lesion (13
) or from patients with clinical signs and symptoms that were not Lyme disease related, we confirmed that the BAT was sensitive (79%) and highly specific (100%). The high sensitivity and specificity were almost identical to those of previous findings (9
). In addition, antimicrobial agents could be easily removed prior to testing with little or no apparent effect on the borreliacidal antibodies. The collective results from previous studies, the CDC evaluation, and this study confirm that the BAT can be used to accurately detect infection with B. burgdorferi
in Lyme disease patients who are evaluated at a primary-care facility.
The results also showed that the BAT was more sensitive and specific than the widely used WB. The potential benefit of the increased accuracy was suggested by the results obtained using the sera from the possible Lyme disease patients. The 40 BAT-positive sera contained high concentrations of borreliacidal antibodies, which eliminated the possibility that the results were due to cross-reactive antibodies. Additionally, these patients had tick exposures, well-accepted symptoms (13
), and no additional findings sufficient to refute a diagnosis of Lyme disease. Thirty (75%) of the 40 BAT-positive sera were positive by the WB, which strengthened further the argument that these BAT-positive patients had Lyme disease. However, 21 (20%) of the WB results were questionable. The decreased sensitivity may have been responsible for the negative WB results for 10 (25%) of the BAT-positive sera. A likely explanation is that these Lyme disease patients had developed an antibody response that was insufficiently diverse to yield reactivities against the multiple proteins necessary for confirmation by WB. In addition, assays of several sera that tested positive by WB and negative by BAT appeared to have yielded false positives. Some sera did not contain borreliacidal antibodies, despite WB-detectable reactivities against multiple species-specific B. burgdorferi
proteins known to induce borreliacidal antibodies (4
). As further support, several patients had inappropriate laboratory results (e.g., IgG antibodies) or clinical or epidemiological findings that suggested an illness other than Lyme disease. Unfortunately, it was impossible to determine with certainty whether the BAT-positive or WB-positive patients were Lyme disease patients, since the B. burgdorferi
infections were not confirmed directly by PCR or culture. However, the high concentrations of borreliacidal antibodies and the absence of contrary clinical findings in the BAT-positive patients provided strong evidence that the BAT could be used alone or in conjunction with WB to increase the accuracy of serodiagnostic confirmation of Lyme disease.
Researchers previously showed that borreliacidal anti-B. burgdorferi
297 antibodies are common in Lyme arthritis patients (9
) but are rarely detected during an early infection (1
). In contrast, borreliacidal anti-50772 antibodies, which are specific for proteins other than OspA and OspB, were detected during all stages of Lyme disease (9
). The results in this study confirmed these findings. Sixty-one (91%) sera contained borreliacidal anti-50772 antibodies, but 6 (9%) sera from patients with long-standing clinical complaints had only borreliacidal anti-297 antibodies. Thus, B. burgdorferi
50772 could be used to confirm most cases of Lyme disease, but the sensitivity of the BAT was maximized by also using B. burgdorferi
The technical complexity of the BAT has hindered widespread use, but the increased sensitivity and specificity should be of sufficient value to warrant availability. The test requires a flow cytometer, live and specific isolates of B. burgdorferi, and removal of antimicrobial agents from sera, but laboratories with experience in flow cytometry could easily perform these tasks. The time required to prepare live organisms, remove antimicrobial agents from sera, set up the test, and evaluate the flow cytometric results is comparable to the time necessary to perform a WB.
In summary, additional prospective studies remain necessary for completely defining the full utility of the BAT. However, our results demonstrate that the BAT is a sensitive and highly specific confirmatory test for Lyme disease that can be used in clinical practice.