New Diagnostic Criteria for Axial Spondylarthritis

CHICAGO—Axial spondylarthritis (SpA) is now the preferred name for a set of diseases including ankylosing spondylitis (AS), an inflammatory disease of the sacroiliac joints and spine. The term, reflecting the expanded diagnostic capabilities available today, emerged after the Assessment of Spondyloarthritis International Society (ASAS) established more inclusive classification criteria for inflammatory back pain (IBP) and SpA.

Diagnosis

The term axial spondylarthritis (or axial spondylarthropathy) is a more inclusive term in that it signifies that a reliable early diagnosis can now be made in the absence of X-ray changes. Magnetic resonance imaging (MRI) can detect sacroiliac inflammation before anything becomes evident on X-rays. This is important because the back pain and stiffness associated with SpA often begin in late adolescence to early adulthood, and patients tend to postpone reporting these symptoms to their physicians. One study has shown that one-third of those patients with early onset pain delay consulting a health care professional for more than 12 months after onset of symptoms, assuming that the symptoms will subside.¹

In addition, early diagnosis is important because therapies that are more effective if used in the early stages of the disorder have become available. These include tumor necrosis factor (TNF) antagonists.

Another diagnostic tool is genetic testing. There is a genetic predisposition to axial spondylarthritis; studies show that at least one-quarter of patients have an underlying genetic risk for SpA.² A positive genetic test for HLA-B27, a major disease predisposing gene, supports a clinician’s diagnosis of SpA in the absence of imaging findings.

This research and its application were addressed in the AHRP Concurrent Session entitled, “Axial Spondylarthritis: New Concepts,” at the 2011 ACR/ARHP Annual Scientific Meeting in November. [Editor’s note: This session was recorded and is available via ACR SessionSelect at www.rheumatology.org.] The session was presented by Muhammad Asim Khan, MD, professor of medicine at Case Western Reserve University School of Medicine and director of Spondylitis Clinic at MetroHealth Medical Center, both in Cleveland. Dr. Khan emphasized that using diagnostic tools and new classification criteria allows a primary care physician to screen potential SpA patients and refer them to a rheumatologist while the disease is still in its early stages.

Dr. Khan differentiated between mechanical pain and inflammatory back pain (IBP) when making a diagnosis. Mechanical back pain is often secondary to overuse of or injury to a normal spine and its supporting structures. On the other hand, IBP characteristics include:

• Insidious onset;
• Pain at night (with improvement upon rising);
• Age at onset less than 40 years;
• Improvement with exercise; and
• No improvement with rest.³

Dr. Khan stated that, “IBP is generally regarded as an important clinical symptom suggesting that the back pain a patient complains about is caused by axial spondyloarthitis. Indeed, about 33% of patients with IBP in primary care have subsequently been diagnosed as having SpA.” However, he warned that there are limitations to using IBP as a diagnostic sign: only approximately 80% of SpA patients versus about 20% of control groups (such as patients with mechanical back pain) also report the same symptoms. “This implies that the presence of IBP alone can never be sufficient to make a diagnosis of SpA but needs to be combined with other clinical, laboratory, and imaging parameters characteristic for SpA,” said Dr. Khan.

These parameters comprise:

• IBP;
• Enthesitis;
• Peripheral arthritis;
• Dacylitis;
• Acute anterior uveitis (AAU);
• Family history of AS, AAU, inflammatory bowel disease (IBD), or reactive arthritis (ReA);
• Psoriasis;
• IBD;
• Good response to nonsteroidal antiinflammatory drugs (NSAIDs);
• Elevated acute phase reactants;
• Presence of HLA-B27; and
• MRI evidence of sacroiliitis.⁴

Dr. Khan narrowed the predominate factors down to four, based on the sensitivity and specificity data compiled by Rudwaleit et al to create the above list: “If a patient has IBP, acute anterior uveitis, a family history of these diseases, and a good response of IBP to NSAIDs, you should strongly suspect that the patient has SpA.”

He also stressed the need for good history taking when a patient has back pain. “The physician has not even touched the patient; yet there is already a high likelihood that the patient has axial spondylarthritis,” said Dr. Khan.

New ASAS Classification Criteria

There are two sets, or arms, of the ASAS criteria: the imaging arm and the clinical arm.⁵ Each set is applied to patients with chronic (more than three months) back pain, the onset of which occurs at less than 45 years of age.

The imaging arm requires only one clinical parameter plus sacroiliitis (X-rays or MRI):

• The sacroiliitis should show definite radiographic disease at grade 2 bilateral or grade 3 to 4 unilateral (according to modified NY criteria 1984); or
• There should be active (acute) inflammation of sacroiliac joints on MRI, highly suggestive of sacroilliitis associated with SpA.

The clinical arm requires a positive HLA-B27 test plus two other clinical parameters, such as:

• IBP;
• Arthritis;
• Enthesitis;
• Uveitis;
• Psoriasis;
• Crohn’s disease/ulcerative colitis;
• Good response to NSAIDs;
• Family history of SpA;
• Elevated C-reactive protein; and
• Presence of HLA-B27.

Management of Axial Spondylarthritis

The first step in managing SpA, said Dr. Kahn, is a three-point approach: patient education, NSAIDs, and physical therapy combined with the development of a lifelong exercise program.

Educating the patient about his or her condition and about actively participating in treatment is crucial. Dr. Khan emphasized that “the word doctor does not mean healer; it means educator. If you don’t educate the patient, you cannot expect compliance” to treatment. The clinician should also encourage the patient to join self-help groups.

NSAIDs decrease spinal and peripheral joint pain and improve function. Prescribing an NSAID that is taken once or twice a day improves compliance. In patients with increased gastrointestinal risk, a gastroprotective agent can be added, or the patient can switch to selective COX-2 inhibitors (coxibs) because they are equally effective.

Exercise, including physical therapy, improves function and decreases pain. Dr. Khan recommended swimming as the best exercise for SpA patients. The exercise should not be short-term but rather the beginning of a lifelong exercise program, which is necessary in the management of a chronic condition.

ASAS recommendations on managing SpA suggest using anti-TNF agents in patients with SpA, but only after:

• A regimen of NSAIDs (at least two different drugs tried for one month or more total);
• An adequate therapeutic trial of a disease-modifying antirheumatic drug (DMARD), preferably sulfasalazine, for patients with peripheral symptoms; and
• An efficacy evaluation of the above steps after 12 weeks.⁶

Note that patients with axial spondylarthritis do not need to take a DMARD before or concomitant with an anti-TNF agent.

All TNF inhibitors are remarkably effective as monotherapy for treating SpA, and the response is even better in early disease. TNF inhibitors have long-term efficacy and an acceptable safety profile, but there is a need for adequate intake of vitamin D and calcium and for ongoing screening for concomitant osteopenia and osteoporosis.

Ann Kepler is a medical journalist based in Chicago.

References

1. Grigg SE, Martin BJ, Buchanan RR, Schachna L. Burden of delay to diagnosis of ankylosing spondylitis. [abstract]. Arthritis Rheum. 2011;63(Suppl 10):1308.
2. Brown MA. The evolving roles of genes and gene expression profiling in ankylosing spondylitis. Ann Rheum Dis. 2011;70(Suppl 3);7.
3. Sieper J, van der Heijde D, Landewé R, et al. New criteria for inflammatory back pain in patients with chronic back pain: A real patient exercise by experts from the Assessment of SpondyloArthritis international Society (ASAS). Ann Rheum Dis. 2009;68:784-788.
4. Rudwaleit M, van der Heijde D, Khan MA, Braun J, Sieper J. How to diagnose axial spondyloarthritis early. Ann Rheum Dis. 2004;63:535-543.
5. Rudwaleit M, van der Heijde D, Landewé R, et al. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): Validation and final selection. Ann Rheum Dis. 2009;68:777-783.
6. Sieper J, Rudwaleit M, Baraliakos X, et al. The Assessment of SpondyloArthritis international Society (ASAS) handbook: A guide to assess spondyloarthritis. Ann Rheum Dis. 2009;68(Suppl II):ii1–ii44.