title: Reply.
authors.affiliation: Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Janneke
authors.initials: J
authors.lastname: de Winter
authors.affiliation: Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Marleen
authors.initials: M
authors.lastname: van de Sande
authors.affiliation: Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Robert
authors.initials: R
authors.lastname: Landewé
authors.affiliation: Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Dominique
authors.initials: D
authors.lastname: Baeten
mesh_terms: D015331:Cohort Studies; D015796:HLA-B27 Antigen; D006801:Humans; D025241:Spondylarthritis; D013167:Spondylitis, Ankylosing
chemical_list: D015796:HLA-B27 Antigen