Background: People with axial Spondyloarthritis (axSpA) suffer from lengthy diagnostic delays of ~7 years. The usage of screening tools to identify axSpA patients in primary care can reduce diagnostic delays by facilitating early referral to rheumatologic care. The purpose of this study was to examine the psychometric properties of a potential screening tool for patients with axSpA.

Method: Content validity was evaluated by soliciting feedback from 7 rheumatologists regarding the relevance and content representativeness of the proposed screening questions. For the test-retest study, participants ≥18 years of age with chronic back pain (≥3 months) without a diagnosis of mechanical or inflammatory back pain (n = 91) were e-recruited through ResearchMatch. Participation included completing identical baseline and follow-up questionnaires ~14 days apart. Weighted quadratic kappa was used to measure test-retest reliability between the two ratings of the ordinal scales. Construct validity was examined using exploratory factor analysis (EFA) and items with factor loadings ≥0.6 were extracted. Scale dimensionality and simplified factorial solutions were measured using Kaiser's criteria (Eigenvalue >1). Cronbach's alpha was used to measure internal consistency.

Results: Most participants were women, non-Hispanic white, and had at least some college education, with a mean age of 45 years. On average, the age at onset of back pain was 31 years. Eleven questions yielded test-retest reliabilities ranging from 0.6 to 0.76. Results from EFA extracted two factors relating to: 1) how pain affects daily life functioning and 2) whether pain improves with movement. Internal consistency was high for questions evaluating how pain affects life, with a Cronbach's alpha of 0.81. Following assessment for validity and reliability, the questionnaire was revised to create the 6-item screening tool.

Conclusions: The 6-item SpA-SED screening tool designed to identify potential cases of axSpA was found to have good test-retest reliability and high internal consistency.