From the Guidelines
Ankylosing spondylitis diagnosis should be based on a combination of clinical evaluation, imaging studies, and laboratory tests, with the Assessment of SpondyloArthritis International Society (ASAS) criteria being the most commonly used diagnostic criteria, as recommended by the 2021 update of the ACR Appropriateness Criteria for inflammatory back pain 1. The diagnosis typically begins with a thorough medical history and physical examination, focusing on symptoms like chronic low back pain that improves with activity, morning stiffness lasting more than 30 minutes, and limited spine mobility. Key features of inflammatory back pain include:
- Insidious onset
- Improvement with exercise
- No improvement with rest
- Occurring at night
- Age of onset <40 years Imaging is crucial, with X-rays showing sacroiliitis (inflammation of the sacroiliac joints) in established cases, while MRI can detect early inflammatory changes before structural damage occurs, as highlighted in the 2017 ACR Appropriateness Criteria for chronic back pain suspected sacroiliitis-spondyloarthropathy 1. Laboratory tests include checking for the HLA-B27 genetic marker, which is present in about 90% of patients with ankylosing spondylitis, though it's not diagnostic on its own, as noted in the 2016 American College of Rheumatology/Spondylitis Association of America/Spondyloarthritis Research and Treatment Network recommendations for the treatment of ankylosing spondylitis and nonradiographic axial spondyloarthritis 1. Inflammatory markers like C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are often elevated but can be normal in some patients. Diagnosis may be delayed because early symptoms can mimic mechanical back pain, and definitive X-ray changes may take years to develop. The ASAS criteria are commonly used, requiring either sacroiliitis on imaging plus one additional spondyloarthritis feature, or HLA-B27 positivity plus two additional features. Early diagnosis is important to begin appropriate treatment and potentially slow disease progression, with treatment algorithms focusing on controlling disease activity and improving quality of life, as emphasized in the 2021 update of the ACR Appropriateness Criteria for inflammatory back pain 1.
From the Research
Ankylosing Spondylitis Diagnosis
- Ankylosing spondylitis (AS) is a disease that can cause early retirement and severe functional disability, with no diagnostic gold standard 2.
- Correct diagnosis depends on a combination of clinical symptoms, signs, and radiological findings, with early detection of inflammation in the sacroiliac joints and spine being crucial 2, 3.
- Magnetic resonance imaging (MRI) has proven useful in detecting early inflammation in the sacroiliac joints and spine 2, 3.
- New classification criteria take into account early sacroiliitis evident on MRI scan, allowing for earlier diagnosis than previously possible 3.
- A comprehensive approach, including a complete history, laboratory testing, and imaging, is necessary to optimize diagnostic accuracy 2.
Clinical Features and Diagnostic Measures
- Morning stiffness lasting more than 30 minutes, sleep disturbance due to back pain, and pain that improves with activity are features suggestive of inflammatory back pain (IBP) 4.
- Nearly two-thirds of primary care healthcare providers reported being the first point of contact for patients with suspected IBP 4.
- Diagnostic blood work, including antinuclear antibody, rheumatoid factor, and human leukocyte antigen B27, is commonly ordered by healthcare providers 4.
- Imaging studies, such as radiography, MRI, or computed tomography, can detect sacroiliitis and are diagnostic for AS in the presence of clinical manifestations 5, 6.
Barriers to Early Diagnosis and Referral
- Lack of adequate specialists nearby, insurance restrictions, and long wait times are barriers to early referral of patients with potential AS 4.
- Many healthcare providers have difficulty identifying features suggestive of IBP and may not refer patients to a rheumatologist in a timely manner 4.
- Delayed diagnosis can result in missed opportunities for early treatment and improved outcomes for patients with AS 5.