The mSQUASH; a valid, reliable and responsive questionnaire for daily physical activity in patients with axial spondyloarthritis.

Aim: Adaptation of the Short QUestionnaire to Assess Health-enhancing physical activity (SQUASH) in order to improve measurement properties in axSpA patients.

Methods: The original SQUASH was adapted using a qualitative stepwise approach with in-depth interviews including healthcare professionals and patients. Content validity was explored by comparing modified-SQUASH (mSQUASH) and original SQUASH.