Diagnosis and management of ankylosing spondylitis

Introduction

Ankylosing spondylitis is a chronic inflammatory rheumatic disorder that primarily affects the axial skeleton. Sacroiliitis is its hallmark, accompanied by inflammation of the entheses (points of union between tendon, ligament, or capsule and bone) and formation of syndesmophytes, leading to spinal ankylosis in later stages. Prevalence estimates vary between 0.1% and 2% in different populations.1 The male:female ratio is around 5:1, and the peak age of onset is at 15-35 years.

Because of its insidious nature, the diagnosis is sometimes delayed until late stages of the disease. Until recently, treatment has been limited to non-steroidal anti-inflammatory drugs and physiotherapy, but the development of cytokine inhibitors that inhibit the activity of tumour necrosis factor α has been an important advance in treatment.

Sources and selection criteria

We searched Medline for clinical trials and reviews using the keywords “ankylosing spondylitis,” “treatment,” “physiotherapy,” “NSAIDs,” “DMARDs,” “anti-TNF,” and “biologics.”

How is it diagnosed?

The most commonly used criteria for the classification of ankylosing spondylitis were developed in 1966 and modified in 1984.²³ They are:

1. Low back pain of at least three months duration with inflammatory characteristics (improved by exercise, not relieved by rest)

2. Limitation of lumbar spine motion in sagittal and frontal planes

3. Decreased chest expansion (relative to normal values for age and sex)

4. Bilateral sacroiliitis grade 2 or higher

5. Unilateral sacroiliitis grade 3 or higher.

Definite ankylosing spondylitis is said to be present when the fourth or fifth criterion presents with any clinical criteria. However, radiological sacroiliitis may not develop for many years, and the development of new criteria (including magnetic resonance imaging) has been proposed to allow confirmation of the diagnosis in patients with early disease (see below).4