GPAtlas🧭 When to suspect
Suspect axial spondyloarthritis (axSpA) – which includes ankylosing spondylitis (radiographic axSpA) and non-radiographic axSpA – in any adult with low back pain and stiffness lasting longer than 3 months that began before the age of 45. The hallmark is inflammatory back pain: pain that improves with movement and worsens with rest, prominent morning stiffness and night pain, distinct from ordinary mechanical back pain.
The single most important message in primary care is that axSpA is routinely missed. The average delay from first symptom to diagnosis is around 8 years, because inflammatory back pain is mislabelled as "mechanical" back pain. It is not simply a young man's disease – it affects women in similar numbers, who tend to wait even longer for a diagnosis.
| Feature | Inflammatory (suggests axSpA) | Mechanical |
|---|---|---|
| Age at onset | < 45 years (often < 35) | Any age |
| Onset | Insidious, gradual | Often acute, after activity or strain |
| Effect of rest | Worse with rest and in the morning | Improves with rest |
| Effect of movement | Improves with exercise | Worsens with activity |
| Night pain | Characteristic – wakes in the second half of the night | Uncommon; little diurnal rhythm |
| Morning stiffness | Prolonged, > 30 minutes | Brief, < 30 minutes |
| Response to NSAIDs | Good, often within 48 hours | Variable |
| Duration | Chronic, > 3 months | Often self-limiting |
Suspicion is strengthened by extra-articular and associated features: acute anterior uveitis (a painful red eye), psoriasis, inflammatory bowel disease, enthesitis (e.g. Achilles or plantar fascia), dactylitis (sausage digit), alternating buttock pain, a first-degree relative with spondyloarthritis, or a recent genitourinary/GI infection (reactive pattern).
NICE provides a clear referral rule. In a person with low back pain that started before 45 and has lasted > 3 months, refer to rheumatology if 4 or more of the following are present; if exactly 3 are present, perform HLA-B27 and refer if positive.
| NICE NG65 – additional referral criteria (need ≥ 4, or 3 + HLA-B27 positive) |
|---|
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• Low back pain that started before the age of 35 |
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• Waking during the second half of the night because of symptoms |
|
• Buttock pain |
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• Improvement with movement |
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• Improvement within 48 hours of taking NSAIDs |
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• A first-degree relative with spondyloarthritis |
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• Current or past arthritis |
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• Current or past enthesitis |
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• Current or past psoriasis |
Source: NICE NG65 · NICE QS170
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