Lack of Association of Group A Streptococcal Infections and Onset of Tics

Background and ObjectivesThe goal of this work was to investigate the association between group A streptococcal (GAS) infections and tic incidence among unaffected children with a family history of chronic tic disorders (CTDs).MethodsIn a prospective cohort study, children with no history for tics who were 3 to 10 years of age with a first-degree relative with a CTD were recruited from the European Multicentre Tics in Children Study (EMTICS) across 16 European centers. Presence of GAS infection was assessed with throat swabs, serum anti–streptolysin O titers, and anti-DNAse titers blinded to clinical status. GAS exposure was defined with 4 different definitions based on these parameters. Cox regression analyses with time-varying GAS exposure were conducted to examine the association of onset of tics and GAS exposure during follow-up. Sensitivity analyses were conducted with Cox regression and logistic regression analyses.ResultsA total of 259 children were recruited; 1 child was found to have tic onset before study entry and therefore was excluded. Sixty-one children (23.6%) developed tics over an average follow-up period of 1 (SD 0.7) year. There was a strong association of sex and onset of tics, with girls having an ≈60% lower risk of developing tics compared to boys (hazard ratio [HR] 0.4, 95% confidence interval [CI] 0.2–0.7). However, there was no statistical evidence to suggest an association of any of the 4 GAS exposure definitions with tic onset (GAS exposure definition 1: HR 0.310, 95% CI 0.037–2.590; definition 2: HR 0.561, 95% CI 0.219–1.436; definition 3: HR 0.853, 95% CI 0.466–1.561; definition 4: HR 0.725, 95% CI 0.384–1.370).DiscussionThese results do not suggest an association between GAS exposure and development of tics.Classification of EvidenceThis study provides Class I evidence that group A streptococcal exposure does not associate with the development of tics in children with first-degree relatives with chronic tic disorder.