The classification and diagnostic criteria of ankylosing spondylitis

doi:10.1016/j.jaut.2014.01.015

Journal of Autoimmunity

Volumes 48–49, February–March 2014, Pages 128-133

https://doi.org/10.1016/j.jaut.2014.01.015 Get rights and content

Abstract

Ankylosing spondylitis is the prototype of immune-mediated inflammatory rheumatic diseases grouped under the term spondyloarthritis (SpA). An early diagnosis has now become increasingly important because effective therapies are available and anti-TNF drugs are even more effective if used in early stages of the disease. In ankylosing spondylitis, the 1984 modified New York criteria have been used widely in clinical studies and daily practice but are not applicable in early disease when the characteristic radiographic signs of sacroiliitis are not visible but active sacroiliitis is readily detectable by magnetic resonance imaging (MRI). Thus there has been a need for new classification or diagnostic criteria to identify inflammatory spondyloarthritis at early stage of the disease. This led to the concept of axial SpA to include the entire spectrum of patients with axial disease both, with and without radiographic damage. New classification criteria for the wider group of SpA have been proposed by ASAS (Assessment of Spondylo Arthritis International Society); and the patients are sub-grouped into (1) a predominantly axial disease, termed axial SpA including AS and non-radiographic axial SpA; (2) peripheral SpA. The clinical course and disease process of non-radiographic axial spondyloarthritis remains unclear. However the development of the SpA criteria by ASAS particularly for axial SpA, is an important step for early diagnosis and better management of these patients.

Introduction

The term ‘spondyloarthritis’ (SpA) designates a group of diseases, which share common clinical and genetic features. These features include involvement of the axial skeleton (sacroiliac joints and spine), peripheral arthritis, enthesitis, dactylitis, acute anterior uveitis, associated psoriasis or inflammatory bowel disease, and presence of the HLA-B27 antigen [1], [2], [3], [4]. Depending on the predominant clinical manifestations, SpA can be classified either as axial SpA (characterized by predominant involvement of the spine and/or sacroiliac joints) or as peripheral SpA (peripheral arthritis, enthesitis, and/or dactylitis) [5], [6]. Axial SpA is characterized by chronic inflammatory back pain and based on clinical and radiological features can be separated into two groups – (i) ankylosing spondylitis (AS), which is defined by the presence of definite structural changes on radiographs in the sacroiliac joints, and (ii) nonradiographic axial SpA which is defined by the presence of sacroiliac inflammation as detected by MRI or the presence of HLA B27 in combination with the presence of features typical of spondyloarthritis. The spectrum of spondyloarthritis is described in Fig. 1. Ankylosing spondylitis is the prototype of immune-mediated inflammatory rheumatic diseases in the axial spondyloarthritis spectrum.

Section snippets

Prevalence of ankylosing spondylitis and spondyloarthritis as a group

Historically, AS was thought to be a disease that almost exclusively affected young men. More recent studies suggest a male-to-female ratio of about 2 or 3 to 1, although there can be considerable geographical and ethnic variation. AS has an estimated prevalence of about 0.5% [7], [8] in the Caucasian population, whereas the estimated prevalence of SpA as a group is about 1.5%–2% [7], [8]. Human leukocyte antigen (HLA)-B27 is strongly linked to disease susceptibility, and there is a close

Clinical features

The most characteristic clinical symptom of AS or axial SpA is inflammatory back pain [1], [2], [16]. The presentation of back pain is not an uncommon occurrence in the general population, making it important to differentiate inflammatory from non-inflammatory causes of back pain. Inflammatory back pain is characterized by stiffness and pain that is worse in the morning or after long periods of inactivity (“gel phenomenon”) and is improved with exercise. Patients commonly complain of difficulty

Diagnostic tests: there are no specific laboratory tests for AS or SpA

There are no laboratory findings that are diagnostic of AS. In contrast to other systemic inflammatory diseases such as Lupus and RA, acute phase reactants (erythrocyte sedimentation rate [ESR] and C-reactive protein) may be normal in majority population of SpA patients [19]. Rheumatoid factor and antinuclear antibodies are absent in SpA.

Almost 90% of the patients with AS [20], [21] and nearly 70% of the patients with axial SpA [21] are positive for HLA-B27 whereas only 6–10% of the general

Diagnosis

In the absence of any diagnostic criteria, the modified New York Classification Criteria are the most widely used tool for the classification of ankylosing spondylitis and they continue to be used for diagnostic purposes too (Table 1) [22]. In most patients, the first symptoms of SpA (usually inflammatory back pain) start in the third or fourth decade of life. As mentioned earlier, inflammatory back is not enough to make the diagnosis; and the diagnosis of AS is based on clinical signs,

Non-radiographic axial SpA – early diagnosis and its importance

Magnetic resonance imaging (MRI) is now considered to be an integral tool to aid in early recognition of inflammation of the axial skeleton, since it can detect active inflammatory changes at the sacroiliac joints with or without structural damage [30]. MRI scan of the SI joints is therefore vital for recognizing axial SpA at the stage when X-ray of the SI joints looks normal. It has been reported that a significant number of these patients will develop radiographic sacroiliitis, that is,

The new assessment of Spondylo Arthritis International Society (ASAS) classification criteria for spondyloarthritis

In contrast to the diagnostic criteria, classification criteria are for case identification for clinical research. Classification criteria are not intended for the diagnosis of individual patients in clinical practice. However, in the absence of true diagnostic criteria, classification criteria are often used for diagnostic purposes which may lead to inappropriate diagnosis. In clinical practice, diagnosis of a condition is dependent upon the prevalence of that condition in the population

Limitations of ASAS classification criteria

The development of the new SpA classification criteria by ASAS is an important step towards a better definition of the early disease stage particularly in axial SpA. Therefore, the criteria can be used for the conduct of studies but also help establish a diagnosis by pointing out features that are highly relevant in SpA. However because of lack of diagnostic criteria, the ASAS classification criteria may be used by physicians inappropriately leading to over diagnosis of axial SpA. The

Conclusion

In recent years, important steps toward standardizing an early diagnosis of SpA have been made, including development of the new “SpA concept” encompassing both the axial and peripheral types, introduction of MRI as one of the key diagnostic imaging tools, development of the new classification criteria for SpA, and application of referral strategies. Further dissemination of these achievements and their consecutive application in clinical practice will contribute to shorten the long diagnostic

Contributions

SPRC and AD have designed the papers and they together have written this manuscript.

Declaration of conflicts of interest

None to declare.

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Published by Elsevier Ltd.

The classification and diagnostic criteria of ankylosing spondylitis

Abstract

Introduction

Section snippets

Prevalence of ankylosing spondylitis and spondyloarthritis as a group

Clinical features

Diagnostic tests: there are no specific laboratory tests for AS or SpA

Diagnosis

Non-radiographic axial SpA – early diagnosis and its importance

The new assessment of Spondylo Arthritis International Society (ASAS) classification criteria for spondyloarthritis

Limitations of ASAS classification criteria

Conclusion

Contributions

Declaration of conflicts of interest

Rheum Dis Clin North Am

Autoimmun Rev.

Rheum Dis Clin North Am

Semin Arthritis Rheum

Best Pract Res Clin Rheumatol

Update on spondyloarthropathies

Ann Intern Med

Association scan of 14,500 nonsynonymous SNPs in four diseases identifies autoimmunity variants

Nat Genet

The development of assessment of Spondyloarthritis International Society classification criteria for axial spondyloarthritis (part I): classification of paper patients by expert opinion including uncertainty appraisal

Ann Rheum Dis

The development of assessment of Spondylo Arthritis International Society classification criteria for axial spondyloarthritis (part II): validation and final selection

Ann Rheum Dis

Prevalence of spondylarthropathies in HLA-B27 positive and negative blood donors

Arthritis Rheum

Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part I

Arthritis Rheum

The risk of developing ankylosing spondylitis in HLA-B27 positive individuals. A comparison of relatives of spondylitis patients with the general population

Arthritis Rheum

HLA-B27 and its subtypes in world populations

Curr Opin Rheumatol

Spondyloarthropathies in Japan: nationwide questionnaire survey performed by the Japan Ankylosing Spondylitis Society

J Rheumatol

Ankylosing spondylitis in sub-Saharan Africa

Postgrad Med J

HLA-B27 and genetic predisposing factors in spondyloarthropathies

Curr Opin Rheumatol

Concordance of disease severity among family members with ankylosing spondylitis?

J Rheumatol

Susceptibility to ankylosing spondylitis in twins: the role of genes, HLA, and the environment

Arthritis Rheum

Primary ankylosing spondylitis: patterns of disease in a Brazilian population of 147 patients

J Rheumatol

Comparison of a high sensitivity and standard C reactive protein measurement in patients with ankylosing spondylitis and non-radiographic axial spondyloarthritis

Ann Rheum Dis