A worldwide team of spondyloarthritis experts published a new set of criteria for classifying the axial form of the disease, an action expected to dramatically expand the number of patients identified with axial spondyloarthritis and enable physicians to flag affected patients sooner and start them on treatment.
A major hope is that earlier treatment, either with nonsteroidal anti-inflammatory drugs (NSAIDs) or tumor necrosis factor (TNF) inhibitors, will help patients by slowing progression of axial spondyloarthritis (SpA). But this anticipated benefit has yet to be supported by study results.
The landmark step in formalizing the early identification of axial SpA was taken by a primarily Eurocentric organization, the Assessment of Spondyloarthritis International Society (ASAS). With the new ASAS classification criteria now published (Ann. Rheum. Dis. 2009;68:770–6; 778–83), it remains unclear whether most U.S. primary care physicians will buy into the criteria and apply them.
The report, published in June, showed that the new classification criteria (see box) identified people with axial SpA with a sensitivity of 83% and a specificity of 84% when tested on 649 patients. The new classification criteria were compared against identification by expert rheumatologists.
If implemented, the new criteria would “increase the frequency of diagnosing [axial SpA] by probably three-fold, to as high as 1.5%” of the adult U.S. population,” said Dr. John D. Reveille, professor of medicine and director of the division of rheumatology and clinical immunogenetics at the University of Texas at Houston.
“The new criteria will be helpful in identifying more patients with the disease, and also for recognizing the disease very early,” agreed Dr. Muhammad A. Khan, professor of medicine at Case Western Reserve University in Cleveland. The old criteria require x-ray evidence of abnormalities in the sacroiliac joints. “With the new criteria, you can make the diagnosis [even] when the x-ray is normal, provided you have MRI evidence,” he said in an interview. Dr. Khan was the sole U.S.-based member of ASAS to serve on the expert panel that devised the new classification criteria.
Axial SpA has typically gone undetected until much later in the course of the disease, when it has progressed to ankylosing spondylitis with its characteristic spinal-bone changes that are visible on plain x-ray films.
“The old classification criteria required patients to have x-ray changes of sacroiliitis, which take 6–10 years to develop after patients have other symptoms,” said Dr. Atul Deodhar, medical director of the rheumatology clinics at the Oregon Health and Science University in Portland. “We definitely need new criteria; we can't call it ankylosing spondylitis if the patient doesn't have x-ray changes,” he said in an interview. “We think that some—but not all—patients with axial spondyloarthritis will progress to ankylosing spondylitis.”
Identification of inflammation in axial joints using MRI is a key element in the new axial SpA classification. Axial joint inflammation is often hard to diagnose without MRI because the affected joints are in locations that are impossible to palpate, Dr. Deodhar said.
He stressed that the appearance of axial joint inflammation on MRI is not enough to make the diagnosis, as this can occur in people without axial SpA. Other key factors include age younger than 45 years, slow onset of symptoms, reduced spine mobility, stiffness and pain that worsens with rest but improves with exercise (unlike mechanical back pain that improves with rest and worsens with exercise), and exacerbation of pain and stiffness while sleeping.
No study results have yet documented that early treatment with an NSAID or with a TNF inhibitor slows or stops progression of axial SpA, but specialists are optimistic that such is the case, and that these data will eventually exist. “We suspect early treatment might have better outcomes; there is the precedent with rheumatoid arthritis,” Dr. Khan said. But even without evidence of slowed progression, early treatment “clearly improves quality of life and function and reduces time lost from work,” Dr. Flynn said.
Features of Axial Spondyloarthritis
Patients with back pain for at least 3 months and with onset younger than 45 years are classified as having spondyloarthritis if they have sacroiliitis on imaging plus at least one spondyloarthritis feature, including:
▸ Inflammatory back pain
▸ Arthritis
▸ Enthesitis
▸ Uveitis
▸ Dactylitis
▸ Psoriasis
▸ Crohn's disease/ulcerative colitis
▸ Good response to NSAIDs
▸ Family history of spondyloarthritis
▸ HLA B27 positive
▸ Elevated C-reactive protein
Source: Ann. Rheum. Dis. 2009; 68:777–83