Measuring outcomes in ankylosing spondylitis: pearls and pitfalls

Patients with ankylosing spondylitis (AS) warrant a comprehensive clinical assessment because of the lack of biomarkers of disease activity, prognosis and response to biologic therapy. Multiple AS-related questionnaires have been developed to assess the disease status accurately, but feasibility remains a problem in clinical practice. The purpose of this review is to assess the pearls and pitfalls of AS-related outcome measures.Single-item questionnaires to measure pain, stiffness and fatigue in patients with AS are easily administrable but may lack a sufficient degree of responsiveness on an individual patient level. The Bath Ankylosing Disease Activity Index remains the gold standard for assessing disease activity in a routine practice, despite poor correlation with C-reactive protein (CRP) levels and MRI inflammation. The Ankylosing Spondylitis Disease Activity Score, a validated and highly discriminatory tool for assessing disease activity in AS, has been developed but lacks feasibility as erythrocytic sedimentation rate and CRP values are often not available during a clinic visit. RAPID-3 appears feasible to assess patients with AS quantitatively over time in busy clinical settings.The assessment of disease status in AS is complex and is impacted by multiple factors. The biggest challenge in AS is to incorporate the disease-specific indices into a routine practice. VIDEO ABSTRACT: http://links.lww.com/COR/A42.