Fibromyalgia in Spondyloarthritis: Effect on Disease Activity Assessment in Clinical Practice.

Objective: Spondyloarthritis (SpA) is the second most frequent inflammatory rheumatic disease, characterized by spinal involvement, peripheral arthritis, or enthesitis with marked pain, stiffness, and fatigue. Fibromyalgia (FM) may be associated with SpA, and shares some common symptoms. We aimed to determine how FM influences assessment of SpA disease activity, which is mainly dependent on patient-based outcome measures such as the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) or the Ankylosing Spondylitis Disease Activity Score (ASDAS).