Axial Spondyloarthritis - A painful needle in the haystack of back pain presentations

How many people do we see with back pain in General Practice? I think it’s safe to say that ‘a lot’ probably covers it. I suspect most of us are acutely aware of the more serious causes of back pain in the older population and potential red flags, notably myeloma or bony mets, but how often do we consider more serious causes in the younger population? What about axial spondyloarthritis? It’s a real ‘needle in the haystack’ scenario. A BJGP review article from earlier this year (BJGP 2025; 75 (752): 136-139) highlights the challenges in the diagnosis of axial spondyloarthritis and some useful principles and advice to help us in primary care.

What’s the problem?

Axial spondyloarthritis (axial SpA) is the preferred term for what we used to know as ankylosing spondylitis and unfortunately delays to diagnosis remain a problem in the UK (as is seen across the world), estimated at 5-9 years. This has a significant impact on outcomes - delayed diagnosis is associated with disease progression, worse function, higher likelihood of work disability and higher healthcare costs. Earlier diagnosis and treatment can help alleviate these burdens, especially since the advent of the newer disease modifying therapies.

Why is this happening?

We are all no doubt aware of one of the major factors here - we see masses of people with back pain, but axial SpA is relatively rare (estimated prevalence in adults in UK 0.3-1.2%). As acknowledged in the BJGP article, picking out the odd case of axial SpA amongst the vast majority of more benign causes is a real challenge in primary care. Alongside this, the depressingly familiar issues of pressure on GP appointments, long delays for imaging (MRI) and secondary care appointments are all important factors. 

Be aware of pitfalls in diagnosis

Whilst we have limited control over the factors above, evidence also suggests that a lack of healthcare professional knowledge of axial SpA, and some pervading myths about presentation and assessment are also factors. Importantly:

• Be aware of gender bias - Axial SpA is sometimes considered a male disease; whilst it is more common in men, the prevalence split is ~2-3:1, and women have lower rates of HLA-B27, all of which contributes to even longer diagnostic delays and poorer outcomes in women.
• HLA-B27 does not make or break the diagnosis - HLA-B27 has poor sensitivity and specificity for axial SpA. About 8% of the normal population carry the HLA-B27 variant, the majority of whom will not develop axial SpA and 10-20% of people with axial SpA will be HLA-B27 negative.
• Other routine GP investigations also have limitations - inflammatory markers and plain X-rays are not infrequently normal in people with axial SpA.

How can we help improve diagnosis rates?

This is the million dollar question. The BJGP article gives some helpful principles alongside the pitfalls above:

• Think about the diagnosis in younger people - patients with axial SpA present young with 92% presenting before the age of 45, and a median presentation of 26 years old.
• Do not rely on investigations given the limitations cited above - focus on clinical features, notably symptoms of inflammatory pain; the ASAS criteria for inflammatory back pain are useful. If ≥4/5 of the following, consider referral or further specialist advice: (1) age at onset ≤40 years; (2) insidious onset; (3) improvement with exercise; (4) no improvement with rest; (5) pain at night (with improvement upon getting up).
• Consider axial SpA in those presenting with back pain and risk factors, notably a family history of spondyloarthritis or personal history of repeat episodes of enthesitis (inflammation of tendons, generally big ones e.g. achilles or patella). 
• Tools to help diagnosis include an online symptom check for patients from NASS, which is then incorporated into a pathway from GIRFT to prompt further questioning and possible use of advice and guidance, and a good summary infographic from the BMJ for the NICE guideline referral criteria is worth looking at.

Ultimately there will be no quick fix for this tricky conundrum, but a hybrid approach of awareness and clinical suspicion particularly in those with risk factors, a focus on clinical features rather than investigations, and use of pathways and tools can all potentially help us pick up cases of axial SpA quicker leading to better outcomes.