1. The Finnish Center for Pediatric and Adolescent Pain Management and Research, Helsinki University Hospital , Helsinki , Finland
2. Department of Rheumatology , Päijät-Häme Central Hospital , Lahti , Finland
3. Folkhälsan Research Center , Helsinki , Finland
4. Primary Health Care Unit , Kuopio University Hospital , Kuopio , Finland
5. Clinicum , University of Helsinki , Helsinki , Finland