Phang JK, Kwan YH, Fong W, et al. - This study was conducted to evaluate the validity and reliability of the Work Productivity and Activity Impairment (WPAI) questionnaire in patients with axSpA. Between 2017 and 2019, researchers included English-speaking individuals seen at a dedicated axSpA clinic in a Singapore tertiary referral hospital. By cognitive debriefing interviews (CDIs), the content validity of the WPAI was estimated. Researchers examined cross-sectional data including a total of 168 individuals (mean [SD] age 41.0 [14.4], 79.8% male). Evidence indicated that presenteeism, overall work productivity loss, and activity impairment showed strong correlations with BASFI, BAS-G, PGA, and pain. This research confirms, in individuals with axSpA, the content validity, construct validity, and test-retest reliability of the WPAI.