The Journal of Rheumatology Volume 78, No. Diagnosing Ankylosing
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The Journal of Rheumatology Volume 78, no. Diagnosing ankylosing spondylitis. Mazen Elyan and Muhammad Asim Khan J Rheumatol 2006;78;12-23 http://www.jrheum.org/content/78/12 1. Sign up for TOCs and other alerts http://www.jrheum.org/alerts 2. Information on Subscriptions http://jrheum.com/faq 3. Information on permissions/orders of reprints http://jrheum.com/reprints_permissions The Journal of Rheumatology is a monthly international serial edited by Earl D. Silverman featuring research articles on clinical subjects from scientists working in rheumatology and related fields. Downloaded from www.jrheum.org on October 1, 2021 - Published by The Journal of Rheumatology Diagnosing Ankylosing Spondylitis MAZEN ELYAN and MUHAMMAD ASIM KHAN ABSTRACT. This article focuses on the early diagnosis and effective management of ankylosing spondylitis (AS), a dis- ease that is not uncommon and that can cause early retirement and severe functional disability. AS, like most other rheumatologic diseases, has no diagnostic gold standard. Correct diagnosis depends largely on a con- stellation of clinical symptoms and signs in addition to radiological findings. Early diagnosis has become all the more important because effective therapies are available: tumor necrosis factor antagonists that suppress disease activity and improve functional ability in patients with AS refractory to conventional drug therapy. The biologic agents are probably even more effective if given early. Inflammation of the sacroiliac joints and the spine is a common, early feature and possibly the most frequent first manifestation of disease. Therefore, its early detection is important, and magnetic resonance imaging has proven useful in this regard. To opti- mize diagnostic accuracy of early disease, it is crucial to use a comprehensive approach and have a deep understanding of the disease and its clinical picture. The clinician should gather a complete history, paying close attention to all the elements of this multisystem disease, as well as judiciously ordering laboratory test- ing and imaging. New strategies are being developed to assist primary care physicians in their screening for these patients, which in turn should result in early referral to rheumatologists and early diagnosis. (J Rheumatol 2006;33 Suppl 78:12-23) Key Indexing Terms: ANKYLOSING SPONDYLITIS DIAGNOSIS IMAGING SPONDYLOARTHRITIS SPONDYLOARTHROPATHIES RADIOGRAPHY INTRODUCTION and effective treatments15. Historically, diagnosis has The hallmark of ankylosing spondylitis (AS), a chronic depended on the finding of radiographic sacroiliitis; systemic rheumatic disorder of indeterminant etiology however, symptoms of AS have been shown to precede (but with a strong genetic predisposition), is sacroiliac radiographic changes by many years16,17. A recent review (SI) joint inflammation (sacroiliitis). AS is the prototype of available evidence concludes that AS can and has to be and most common member of a group of diseases called diagnosed earlier, and that AS can be diagnosed prior to the spondyloarthropathies (SpA), which also includes emergence of definite radiological changes18. reactive arthritis, psoriatic spondyloarthritis, spondy- loarthritis of inflammatory bowel disease, and undiffer- UNDERDIAGNOSIS entiated spondyloarthritis1. Their prevalence varies The diagnosis of AS or other related SpA is often missed among ethnic and racial groups; in Europe this ranges or markedly delayed18, especially in a primary care set- from 0.1% to 1.4%; however, a more consistent number ting19. A physician who is not fully aware of the clinical approaches 0.5%2-11. These data suggest that AS and presentation of AS might overlook this diagnosis when a related SpA may be as common as rheumatoid arthritis teenager or a young adult presents with chronic back (RA). Unlike RA, AS typically starts during the late pain, even though this is a very typical presentation. One teens and early twenties; however, the overall socioeco- reason is that back pain is very prevalent in the general nomic impact of both disease groups on the patient and population, while AS or other related SpA are not the society are about equal1,12-14. most common cause of back pain. Moreover, in many The early correct diagnosis of AS is important in order patients with AS, it may take years from onset of inflam- to decrease disease burden through early intervention to matory back pain to development of radiographic reduce disability experienced by many patients. Early sacroiliitis, despite inflammation as detected by magnetic diagnosis is more important now with availability of new resonance imaging (MRI) and despite clinical manifesta- tions such as back pain and stiffness. For example, in a From the Division of Rheumatology, Case Western Reserve University, study of patients with symptoms and signs consistent MetroHealth Medical Center, Cleveland, Ohio, USA. with early AS [inflammatory back pain, plus additional features of peripheral arthritis, heel pain, or acute uveitis; Funding for this supplement series was provided by Amgen, Inc. and Wyeth Research. or elevated levels of C-reactive protein (CRP) and ery- throcyte sedimentation rate (ESR) but radiographically M. Elyan, MD; M.A. Khan, MD, MACP. normal sacroiliac joints], 36% developed radiographic evidence of sacroiliitis in 5 years and 59% did so in 10 Address reprint requests to Dr. M.A. Khan, Division of Rheumatology, 16 Case Western Reserve University, MetroHealth Medical Center, 2500 years . This was also shown in a study of HLA-B27-pos- MetroHealth Drive, Cleveland, OH 44109-1998. E-mail: itive relatives of patients with AS9, where radiographic [email protected] 12 The Journal of Rheumatology 2006, Volume 33 Supplement 78 Downloaded from www.jrheum.org on October 1, 2021 - Published by The Journal of Rheumatology Figure 1. The concept of axial spondyloarthritis, showing the transition from early to late stages of axial spondyloarthritis. Symptoms of axial spondyloarthritis usually start before sacroiliitis can be seen on plain radiographs, but over years, sacroiliitis and possi- bly syndesmophytes will be visible. Back pain as the main symptom may be present throughout the disease course. The broken line marks the separation, according to estab- lished criteria, to distinguish axial undifferentiated spondyloarthritis without radi- ographic changes from ankylosing spondylitis. During early years, MRI can detect inflammatory changes of sacroiliitis before they become evident on plain radiographs. Modified from Rudwaleit, et al. Arthritis Rheum 2005;52:1000-8, with permission. sacroiliitis was found in 16% of patients younger than 45 validated diagnostic criteria exist28. Classification criteria years and in 38% of patients older than 45 years. In exist, but they are used to ensure patients enrolled in clin- another family study, radiographic evidence of sacroiliitis ical studies have a firm diagnosis and are a homogeneous was found in 40% of patients with SpA with duration of group and are inappropriate for clinician diagnosis. symptoms of 10 years, in 70% with symptoms for 10 to 19 Because classification criteria are designed to be highly years, and in 86% with symptoms for 20 years or more20. specific, they may not be sensitive enough to establish Recent use of MRI has confirmed that active inflamma- diagnosis at an early stage of disease. tion of the sacroiliac joints and/or the spine is present The 1961 Rome criteria were the first criteria developed long before the appearance of unequivocal sacroiliitis on for classification of AS; at later evaluation, thoracic pain plain radiography (Figure 1)18,21. Therefore, the absence and uveitis were removed owing to either low specificity of radiographic sacroiliitis during the early years of dis- or sensitivity, resulting in the 1966 New York classifica- ease should certainly not be used to rule out the diagno- tion criteria29. In 1977, criteria for chronic inflammatory sis, especially when the presence of inflammation can be back pain were proposed to help differentiate it from detected by other imaging modalities, such as MRI. other causes of chronic back pain30. In 1984, the modi- The average delay in diagnosis can vary from 3 to 11 fied New York criteria26 were proposed, incorporating years from onset of symptoms, depending on the type of the inflammatory back pain concept. symptoms and the clinical training of the physician13,22- According to the modified New York criteria, a patient 26. This delay is relatively longer in women than in men27, can be classified as having definite AS if at least 1 clinical in children and adolescents than in older patients27, and criterion (inflammatory back pain, limitation of mobility in HLA-B27-negative patients than in HLA-B27-positive of the lumbar spine, or limitation of chest expansion), patients13,26. The longer the diagnosis is delayed, the plus the radiologic criterion, are met (Table 1). The mod- worse the functional outcome may be, especially with ified New York classification criteria are currently the juvenile-onset AS27. most commonly (and inappropriately) used for establish- ing the diagnosis of AS in clinical practice. Challenges identifying AS. AS, like most other diseases, Another challenge to early diagnosis is the insidious does not have a diagnostic gold standard. Correct diag- onset of the disease, and symptoms can often be mild and nosis largely depends on a constellation of clinical symp- nonspecific during the early stage. Many cases of early toms and signs, in addition to radiologic