The use of local isolates in Western blots improves serological diagnosis of Lyme disease in Scotland.

Nine Scottish Borrelia burgdorferi isolates were investigated in IgG Western blot tests. Sera previously found to be positive and negative when tested by routine Western blots prepared from reference strain B. burgdorferi sensu stricto antigen had different outcomes with these isolates. Two isolates, E5 (Borrelia afzelii) and G4 (B. burgdorferi sensu stricto) performed well, reproducing Western blot-positive results in 90 and 95% of tests, respectively. When antigens from both isolates were incorporated into a single IgG Western blot, the results of a panel of sera were improved when compared to the routine reference strain IgG Western blot. All of the sera positive by the routine Western blot remained positive using the Scottish isolate antigen mix. Twenty-three of the 25 negative sera remained negative and two produced an equivocal result. Of the 15 samples that tested IgG Western blot equivocal with the B. burgdorferi sensu stricto reference strain, 11 (73%) became weak or strong positive when tested with the B. afzelii/B. burgdorferi sensu stricto antigen mix (chi(2)=14.35, Yates' correction, P<0.001). In seven of these, a clinical picture of Lyme disease was consistent with the new results. The use of Scottish strains of B. afzelii and B. burgdorferi sensu stricto to provide antigen for the IgG Western blot improves the diagnosis of Lyme disease for patients in Scotland.