Inflammatory back pain is often mistaken for mechanical back pain, and rheumatologists say this is leading to misdiagnosis and delays in appropriate treatment.
Inflammatory back pain might account for as much as 5% to 10% of chronic back pain in the community, experts at a recent educational event for GPs and physiotherapists in Sydney said earlier this month.
Without an early diagnosis, patients will not only suffer with pain for longer, but risk the underlying condition worsening over time.
Speaking at the seminar for GPs, run by BJC Health, rheumatologists Dr Yuen Leow and Dr Herman Lau said it was important to be alert to the key signs of inflammatory back pain and the many ways it could present.
While diagnostic technology has improved, clinicians still face a challenge in identifying the conditions causing inflammatory back pain, which included conditions such as ankylosing spondylitis, psoriatic arthritis and reactive arthritis.
But broadly speaking, Dr Lau and Dr Leow said axial spondyloarthritis fell into two categories: radiographic and non-radiographic.
Though the symptoms may be similar across the two, patients with non-radiographic axial spondyloarthritis have a clinical picture of ankylosing spondylitis but no radiographic sacroiliitis.
While patients with ankylosing spondylitis usually start with a diagnosis of non-radiographic spondyloarthritis, Dr Lau said that roughly one in five of those would progress to having radiographic features over a two-year period. This essentially meant the management should be almost the same, he said.
The Sydney rheumatologists gave some quick tips for doctors wanting to differentiate inflammatory from mechanical back pain.
Inflammatory back pain was more commonly found in patients aged under 40. It tended to have an insidious onset of pain that improved with movement. Morning stiffness lasting 30 minutes or more was a feature, and patients with inflammatory back pain often reported NSAIDs working “like magic”, Dr Lau said.
On the other hand, the onset of mechanical back pain was often acute, could happen at any age, tended to worsen with movement and had a variable response to NSAIDs.
Dr Lau said that it was important to exclude red flags such as a change in bladder or bowel function, fever or a history of malignancy which “usually pointed to something more sinister”.
Patients with inflammatory back pain were more likely to also present with hip and shoulder joint involvement, tendonitis and symptoms relating to their peripheral joints and chest wall.
Other common features were extraarticular manifestations, such as uveitis, cardiopulmonary symptoms, osteoporosis, fatigue and psychosocial symptoms.
“If someone has more than just back pain, and has these other features as well, then consider more systemic condition like spondyloarthritis,” Dr Lau said.
When it came to a quick diagnosis, Dr Lau also noted that the location of the pain often began in the sacroiliac joints in the lower part of the back, which was actually in the gluteal area.
“So when [GPs] order imaging studies to look for inflammatory spinal disease, they always have to ask for sacroiliac joints, because that’s often forgotten,” he said.