What are the key clinical features that differentiate axial spondyloarthritis from other forms of back pain?

Key clinical features that differentiate axial spondyloarthritis from other back pain include:

• Inflammatory back pain that started before the age of 45 years and lasted longer than 3 months, especially if it started before age 35, with symptoms such as waking during the second half of the night due to symptoms, buttock pain, and improvement with movement and NSAIDs ¹.
• Presence of additional features such as current or past arthritis, enthesitis, psoriasis, or a family history of spondyloarthritis or psoriasis, which increase suspicion ¹.
• Imaging evidence of sacroiliitis meeting the modified New York criteria on X-ray or MRI showing inflammation consistent with axial spondyloarthritis ¹.
• HLA‑B27 positivity, although axial spondyloarthritis can occur in HLA‑B27 negative individuals ¹.