Moving instead of asking? Performance-based tests and BASFI-questionnaire measure different aspects of physical function in ankylosing spondylitis
Salima FE van Weely*, J Christiaan van Denderen, Martijn PM Steultjens, Marike van der Leeden, Michael T Nurmohamed, Joost Dekker, Ben AC Dijkmans and Irene E van der Horst-Bruinsma