OBJECTIVE: Inflammatory back pain (IBP) is an important feature of axial spondyloarthritis (SpA) that is poorly recognized in primary care, perhaps delaying diagnosis of SpA. We aimed to develop and validate a self-report questionnaire using important domains reported by patients with IBP. METHODS: We developed a 6-item questionnaire assessing spinal/hip stiffness, nocturnal pain, diurnal variation, effects of exercise/rest, and peripheral joint pain/swelling. This was compared with the Calin questionnaire and the domains comprising the Assessment of Spondyloarthritis International Society (ASAS) criteria for IBP in 220 patients with established axial SpA and 66 patients with mechanical back pain followed in tertiary care rheumatology clinics. The classification utility of each item was evaluated using sensitivity, specificity, and likelihood ratio (LR). Multivariable logistic regression was used to analyze different combinations of items to develop candidate scoring systems. RESULTS: The single item "diurnal variation" had the highest combination of sensitivity (49%) and specificity (92%) for IBP (positive LR 5.95, 95% CI 2.54-13.94), outperforming the Calin and ASAS IBP criteria, which had sensitivities of 83% and 59%, specificities 42% and 66%, positive LR 1.42 and 1.72, negative LR 0.41 and 0.62, respectively. Classification utility of this item was even higher in SpA patients with disease duration < 6 years (sensitivity 48%, specificity 96%, positive LR 12, negative LR 0.54). The other 5 items did not improve classification utility in any combination. CONCLUSION: Assessment of a single self-reported item, "diurnal variation," had substantial classification utility for IBP. This domain is not addressed in existing criteria for IBP, indicating a potentially important omission.
OBJECTIVE:Inflammatory back pain (IBP) is an important feature of axial spondyloarthritis (SpA) that is poorly recognized in primary care, perhaps delaying diagnosis of SpA. We aimed to develop and validate a self-report questionnaire using important domains reported by patients with IBP. METHODS: We developed a 6-item questionnaire assessing spinal/hip stiffness, nocturnal pain, diurnal variation, effects of exercise/rest, and peripheral joint pain/swelling. This was compared with the Calin questionnaire and the domains comprising the Assessment of Spondyloarthritis International Society (ASAS) criteria for IBP in 220 patients with established axial SpA and 66 patients with mechanical back pain followed in tertiary care rheumatology clinics. The classification utility of each item was evaluated using sensitivity, specificity, and likelihood ratio (LR). Multivariable logistic regression was used to analyze different combinations of items to develop candidate scoring systems. RESULTS: The single item "diurnal variation" had the highest combination of sensitivity (49%) and specificity (92%) for IBP (positive LR 5.95, 95% CI 2.54-13.94), outperforming the Calin and ASASIBP criteria, which had sensitivities of 83% and 59%, specificities 42% and 66%, positive LR 1.42 and 1.72, negative LR 0.41 and 0.62, respectively. Classification utility of this item was even higher in SpA patients with disease duration < 6 years (sensitivity 48%, specificity 96%, positive LR 12, negative LR 0.54). The other 5 items did not improve classification utility in any combination. CONCLUSION: Assessment of a single self-reported item, "diurnal variation," had substantial classification utility for IBP. This domain is not addressed in existing criteria for IBP, indicating a potentially important omission.