Other pathogens?
Although the results showed no association between strep and tics in this population, it does not “close the door completely” on a potential relationship, said Dr. Schrag.
“By and large, the development of tics in children is not associated with group A strep, but differences in small subgroups can never be excluded by a study like this.”
Participants in this study were part of the European Multicentre Tics in Children Studies (EMTICS), a prospective cohort study exploring the role of environmental and genetic factors in pediatric CTD. That project is also looking at immune system factors, “which might play a role in the development of chronic tic disorder and associated conditions,” said Dr. Schrag.
It’s still possible, she added, that other pathogens could play a role in tic development. “That’s going to be the subject of further analysis and future studies,” she said.
Tamara Pringsheim, MD, professor of clinical neurosciences, psychiatry, pediatrics, and community health sciences, University of Calgary (Alta.), praised the research.
“This was a well-designed study, with a large sample of 260 children followed for up to 4 years, using a standardized protocol to assess for group A streptococcal infection and new onset of tics.”
The study, which did not uncover an association between GAS exposure and tic onset, “provides high level evidence that group A streptococcal exposure is not an important risk factor for the new onset of tics in children with a family history of tic disorders.”
The study received funding from the European Union Seventh Framework Program for research technological development and demonstration. Dr. Schrag reports receiving consultancy or advisory board honoraria from Biogen, Abbvie, Bial, and Neurotechnology; research support from the National Institute of Health Research, Parkinsons UK, and the Economic and Social Research Council and the European Commission; and Royalties from Oxford University Press. Dr. Pringsheim reports no relevant financial relationships.
A version of this article first appeared on Medscape.com.