RESIDUAL SEROLOGIC REACTIVITY IN CHILDREN WITH RESOLVED LYME ARTHRITIS

Objective. To define the pattern of persistent antibody response in ch ildren with resolved Lyme arthritis. Methods. From a cohort of 67 chil dren with Lyme arthritis followed in bur department since 1989; 19 wer e selected using these criteria: All patients (1) were asymptomatic; ( 2) had an ELISA titer less than or equal to 1:160; (3) had been in tre atment a minimum of 6 months. Their initial and late samples were asse ssed by Western blot and the pattern of reactivity was analyzed. Resul ts. The mean interval between treatment and last sample was 9.6 months (6-23). Analysis of the last sample showed that only 5/19 were negati ve by ELISA and 4/19 were at the cutoff limit (1:XO). Only 6 patients had fewer than 4 reactive bands, 4 had 4 bands, and 9 had 5-11 bands o n Western blot. The 41, 39, and 60 kDa were the most commonly observed reactive bands at last evaluation. 31 and 34 kDa bands, while relativ ely common in initial samples (36%), became uncommon (5%) on late samp les. A significant finding was the absence of IgM reactivity in 18/19: 1/19 had 41 kDa reactivity. Only 4 patients had both ELISA (<1:80) an d Western blot tests negative (<5 reactive bands). Conclusion. All pat ients with resolved Lyme arthritis continue to show serologic reactivi ty beyond 6 months of therapy. 68% of the patients satisfy Western blo t criteria for positivity in bur laboratory. IgM reactivity to any ant igen was minimal and IgG reactivity against the 41 kDa antigen, consid ered diagnostic of infection in initial samples by some laboratories, is very common (16/19).