Enhanced Sensitivity of the Borreliacidal-Antibody Test

Letters Enhanced Sensitivity of the Borreliacidal-Antibody Test To the Editor: We thank Dr. Agger and Ms. Ca se for confirming the exce ptional specificity of the borreliacidal-antibody test (BAT; also known as the Gundersen Lyme test) for the serodiagnosis of Lyme disease (LD) in their article published in the J une 1997 issue of the Mayo Clinic Proceedings (pages 510 to 514) . Th e authors did not, however, discuss published da tal on the enhanced sensitivity of the test. The authors repo rted a sensitivity of II % in early LD when the BAT was performed with use of Borrelia burgdorferi strain 297 . In a previous investigation, I we reported a com parab le sensitivity of 15% when only B. burgdorferi strain 297 was used . Th is low sensitivity of borreliacidal antibody detection in early LD is not surprising because we have also shown that level s of borreliaci dal activi ty aga inst B. burgdorferi strain 297 increase with the severi ty and dura tion of infection.' When B. burgdorfe ri stra in 50772 was used instead of 297, however, borreliacidal antibodies were detectable in 72% of these same early LD serum samples . I When the results from both strai ns were combined, the se nsitivity of the BAT was 77%. By includ ing B. burgdorferi strain 50772 , the sensitivity of the BAT in early LD increase d more than fivefold. Of more importance, the sensitivity was almost threefold hi gher than that obtained with enzyme-linked immunosorbent assay (ELISA).' The increased sensitivity observed when B. burgdorferi strain 50772 is used for the BAT is easily exp lained . The outer surface of B. burgdorferi strain 297 is co mpri sed primarily of outer surface protein (Os p) A and B. Recently, Schwan and associates) demonstrated significant dow n-regu lation of OspA and OspB express ion and up-regulation of other B. burgdorfe ri protein s, especially OspC , shortly afte r the body temper ature of an infec ted tick increases . Borreliacidal antibodies in ear ly LD serum samples are pr ob ably directe d aga ins t th ese tem pe ratu re- re gul at ed B. burgdorferi proteins. In fact, anti-OspA and anti-Os pB antibody respon ses are most often detectab le in late LD .' Th us, OspA and OspB on the surface of B. burgdorferi strain 297 likely hinder the interaction of borreliacidal antibodies with other Osps in early LD. B. burgdorferi strai n 50772 , which does not e xpress OspA or Osp B, is more sensitive to killing by non -OspA or non-Osp B borreliacidal antibodies. Moreover, the use of flow cytometry for the detection of borreliacidal antibod ies contributes to the enhanced sensitivity by allow ing an objective determ ination of borre liaci dal activity against small numbers (10") of B. burgdorferi organisms.' In addition to high sensitivity, we have also demonstrated the high speci ficity of borreliacidal antibodi es.' No anti -strai n 297 borrelia cidal antibodies were detected in 114 serum sam ples from patients with other potentially cros s-reactive illnesses . Thi s finding was in direc t contrast to those obtained with imm unofluorescence assay (IFA) and ELISA, which yiel ded false-positive resu lts in 39% and 45% of these samples , respectively. Agger and Case confirmed these results: they reported low percen tages of false-pos itive results with the BAT in patients with other illnesses. In contrast, IFA and ELISA frequentl y demonstrated false-positive results (20.0 to 51.3 %) in both acute and chro nic non -LD infections and noninfec tiou s inflammat ory conditions. We have also previously demonMayo Clin Proc 1997;72:1093-1095

strated the exquisite speci ficity of borrel iacid al antibod ies detectable with use of B. burgdorfe ri strain 507 72 . 1 No borreliacidal activ ity again st strain 50772 was detected in 143 of 145 serum samples (98 .6%) from normal co ntrol subjec ts or patient s with other pote ntially cross -reactive illnesses. Thus, the BAT is high ly sensitive and specific when B. burgdorferi strains 297 and 50772 are used. Collectivel y, the results reported by Agger and Case and olhers l •2..5 confirm that the BAT is a sensit ive and highly speci fic confirmatory test for LD. The Gu ndersen Medical Foundation , a division of Gu nder sen Lutheran Medic al Ce nter, has patented this test procedure. Drs. Callister and Schell are the inven tor s of the test and will financial ly benefit from its success ful commercializatio n. The co authors of their pubficatio ns'f" have no vested interest in this test procedure. Steven M. Calli ster, Ph.D. Section of Infec tious Disease Gu nderse n Luth eran Medical Center La C rosse, Wisconsin Ronald F. Schell, Ph.D. Wiscons in State Laboratory of Hygiene Department of Med ical Microbiol ogy and Immunology Unive rsity of Wisconsin Medical School Mad ison, Wisconsin Steven D. Lovrich, Ph.D. Microbiology Research Laboratory Gundersen Medical Foun dation La Crosse, W iscon sin REFERENCES I. Callister SM. l obe DA, Schell RF, Pavia CS, Lovrich SD. Sensitivity and specificity of the bcrre liacida l-anribody lest during ear ly Lyme disease: a ' go ld standard' ? Clin Diagn Lab Imm unol 1996;3:399-402 2. Callister SM , Schell RF, Case KL. Lovric h SD, Day SP. Chara cteriza tion of the borreliacidal antibody response to Borrelia burgdorferi in humans: a scrodia gnostictest. JInfect Dis t 993;167:158-164 3. Sch wan TG , Piesman 1, Go lde wr, Dolan MC, Rosa PA. Induction of an outer surface protein on Borrelia burgdorferi during tick feeding. Proc atl Acad Sci U S A 1995;92:2909-291 3 . 4. Barbour AG, Burgdo rfer W, Grunwald t E, Steere AC. Antibodies of patients with Lyme disease 10 components of the Ixodes damm ini spiroc hete. 1 Clin Invest 1983;72 :504 -5 15 5. Callister SM, Schell RF, Lim LCL, l obe DA, Case KL, Bryant G L, et al. Detection of borre liacidal antibod ies by flow cytornetry: an accurate, highly specific serodiagnostic test for Lyme disease. Arch Intern Med 1994: 154:1625-1632

III response: We apprecia te the oppo rtunity to respond to the points raised by Callister, Schell, and Lovric h. During the summer of 1992 (when the serum samples we reviewed were collected) and the approximately 2-year period before the retrospec tive chan re view reported in our article, the borreliacidal antibody test (BAT), performed with use of Borrelia burgdorfe ri strai n 297 under Dr. Ca llister' s supervision in the research laboratory at Gundersen Lut heran Med ical Center, was the met hod described by these re-

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