Background/Purpose: Several strategies for distinguishing Ankylosing Spondylitis (AS) and Axial Spondylarthritis (axSpA) from other conditions have been proposed but have only been studied in the context of chronic back pain. Prior strategies have not been evaluated in the context of an unselected rheumatologic population where the prevalence is lower and/or in older age groups. This study evaluates a psychometrically distinct patient questionnaire in an unselected population that includes patients without back pain and those with fibromyalgia.

Methods: The study comprised of 490 consecutive, unselected new patients referred to 4 academic rheumatology outpatient clinics in the period 2011-12. Patients completed a questionnaire prior to clinical evaluation. Inability to obtain informed consent in the English language was the only exclusion criterion. Patients were followed for 6 months from the baseline visit. Protocol specified gold standard for AS and axSpA diagnosis was the rheumatologist assessment (blinded to the results of the questionnaire) based on the history, physical examination, radiographs, and laboratory testing and appropriate work up. Questionnaire summary scores were converted to Z-scores.

Results: The mean (range) age of the study population was 48 (18-91) years; 74% were women. Of the 490 patients 102 tested positive by the questionnaire using original cut off values and 22 received a rheumatologist diagnosis of AS (prevalence 4.4%) and 36 were diagnosed with axSpA (prevalence =7.4%). Results of ROC analyses are shown in Table 1. The areas under the curve for AS and axSpA for patients with and without back pain were 0.74, 0.67, 0.84,0.75 respectively

Table 1. Receiver Operator Curve Analysis for patients with AS and axSpA with and without back pain

Conclusion: With adjustments to the score cut-offs, the evaluated patient questionnaire may be used either as a sensitive screening tool or as a specific diagnostic aid in assessing AS and axSpA in non-selected patient populations.