Axial Spondyloarthritis: Are We Missing the Diagnosis?
Lead Author Joel D. Taurog, MD Comments
Providers who treat back pain often lack a clear understanding of the presentation, diagnostic workup and treatment options for axial spondyloarthritis (SpA), according to a paper recently published in The New England Journal of Medicine.
Joel D. Taurog, MD, Burnett Professor for Arthritis Research at the University of Texas Southwestern Medical Center discussed with SpineUniverse this lack of understanding stating, “Individuals with axial spondyloarthritis frequently go for many years being misdiagnosed and inappropriately treated before being referred to a rheumatologist.” The prevalence of axial SpA, of which ankylosing spondylitis is a subset, is similar to that of rheumatoid arthritis, highlighting the clinical importance of the paper’s main finding.
Background and History
Magnetic resonance imaging (MRI) in the 1990s helped to solidify the understanding that spinal and sacroiliac inflammation occurs before definitive sacroiliitis can be demonstrated on radiographs. In 2000, TNF inhibitors were found to be dramatically effective in alleviating the symptoms of ankylosing spondylitis, advancing efforts in diagnosing and classifying early disease.
Inflammatory back pain has a 70% to 80% sensitivity as a diagnostic indicator for axial SpA. Common signs and symptoms of inflammatory back pain include dull lower back and buttock pain of insidious onset that is initially intermittent but persistently progresses. The pain diminishes with activity but can return with inactivity and is associated with morning stiffness of 30 minutes or more.
Additionally, according to Dr. Taurog, nocturnal exacerbation of pain is common, “Particularly during the second half of the night, forcing the patient to rise and move around.” He adds that pain is often present in the thoracic spine as well. “Cervical involvement typically occurs late but can predominate. Pain in the chest occurs in more than 40% of patients with spondyloarthritis.”
The Assessment of SpondyloArthritis International Society (ASAS), developed in 2009, includes classification criteria from imaging, clinical, and laboratory findings and helps define the concept of axial SpA. According to the authors, “These criteria are fulfilled in persons who have had back pain for 3 or more consecutive months before reaching 45 years of age, who have had the presence of sacroiliitis confirmed on MRI or plain radiography, and who have at least one clinical or laboratory finding that is characteristic of spondyloarthritis.”
As an alternative to these imaging criteria, patients with a positive HLA-B27 test with two or more clinical or laboratory findings also fulfill the criteria for axial SpA. Dr. Taurog added, “It is important to emphasize that these are classification criteria intended for clinical research and therapeutic studies but are not diagnostic criteria.”
An MRI is indicated in the workup of axial SpA if x-rays are negative for sacroiliitis, or they are contraindicated, and the diagnosis cannot be made solely on clinical grounds. According to the authors, “the presence of subchondral or periarticular bone marrow edema in sacroiliac joints on fat-saturated T2-weighted or short-tau inversion-recovery (STIR) sequences,” are required by ASAS to confirm diagnosis of axial SpA.
However, there is a significant concern for false negatives on MRI due to the low sensitivity for sacroiliac and spinal inflammation in protocols commonly used for the evaluation of chronic lower back pain. When asked whether “rule out axial SpA” was sufficient to use on the MRI order, Dr. Taurog replied, “Many spine MRIs are interpreted by neuroradiologists, many of whom are not focused on inflammation. The more specific you can be on what you are looking for, the better. Detailed communication between the clinician and radiologist is important, and working with a musculoskeletal radiologist is preferable.”
“Many individuals with axial spondyloarthritis will have a history of peripheral arthritis or enthesitis (inflammation at ligamentous attachments to bone such as the Achilles tendon insertion), and this can be a clue that the back pain is part of systemic inflammatory disease,” Dr. Taurog noted.
Patients with definite ankylosing spondylitis have an estimated 10% lifetime risk of spinal fracture. This can lead to “a high risk of devastating spinal cord injury,” the authors report.
According to the researchers, treatment goals for axial spondyloarthritis include “reducing symptoms, improving and maintaining spinal flexibility and normal posture, reducing functional limitations, maintaining the ability to work, and decreasing the complications associated with the disease.”
NSAIDs are the “first-line of drug treatment for pain and stiffness” without individual preference concerning efficacy. When NSAIDs are not sufficient or side effects are intolerable; TNF inhibitors are strongly recommended.
When asked whether either drug category was superior Dr. Taurog told SpineUniverse that “all the of the studies of TNF inhibitors showed their superiority over NSAIDs in terms of reducing symptoms since most of the placebo patients were also taking NSAIDs. TNF inhibitors are clearly superior for reducing inflammation seen on MRI.” He then concluded, “There is some suggestion that NSAIDs may be better at preventing radiographic progression (erosions and syndesmophytes), but this is not proven.”