Spondylitis Testing: Understanding Diagnosis, Methods, and Interpretation

What is spondylitis test?

A "spondylitis test" is not a single, definitive test but rather a comprehensive diagnostic process involving a combination of clinical examinations, laboratory tests, and imaging studies used by healthcare professionals to diagnose spondylitis, particularly Ankylosing Spondylitis (AS), which is a chronic inflammatory condition primarily affecting the spine and sacroiliac joints.

Understanding Spondylitis

Spondylitis refers to inflammation of the vertebrae, the bones that make up the spine. The most common and widely recognized form is Ankylosing Spondylitis (AS), a type of inflammatory arthritis that primarily affects the axial skeleton (spine and sacroiliac joints), but can also impact other joints, eyes, bowel, and lungs. Unlike mechanical back pain, spondylitis pain typically worsens with rest and improves with activity, often presenting with morning stiffness that lasts for more than 30 minutes.

Why is Spondylitis Testing Performed?

Testing for spondylitis is initiated when an individual presents with persistent symptoms suggestive of inflammatory spinal pain. These symptoms often include:

• Chronic back pain: Especially in the lower back and buttocks, lasting more than three months.
• Morning stiffness: Significant stiffness that improves with exercise and worsens with inactivity.
• Pain at night: Waking from sleep due to back pain, particularly in the second half of the night.
• Alternating buttock pain: Pain that shifts between the left and right buttocks.
• Fatigue: Persistent tiredness.
• Peripheral joint pain: Pain and swelling in other joints like hips, knees, or shoulders.
• Enthesitis: Pain where tendons or ligaments attach to bone, common in the heel or Achilles tendon.

Early diagnosis is crucial for effective management, as it allows for timely intervention to slow disease progression, reduce pain, improve function, and prevent severe structural damage and spinal fusion (ankylosis).

Components of Spondylitis Testing

The diagnostic process for spondylitis is multifaceted, combining a thorough clinical assessment with specific diagnostic tools. No single test can definitively diagnose spondylitis; rather, a rheumatologist or physician interprets a combination of findings.

Clinical Examination

A physical examination is the first and most critical step. The healthcare provider will assess posture, spinal mobility, tenderness, and range of motion. Specific maneuvers are performed to evaluate the spine and sacroiliac (SI) joints for signs of inflammation or limited movement.

• Schober's Test: This test measures lumbar spine flexion. The examiner marks a point 10 cm above and 5 cm below the dimples of Venus (PSIS) on the lower back. The patient is asked to bend forward as far as possible. In a healthy individual, the distance between the two marks should increase by at least 5 cm. A smaller increase suggests reduced lumbar mobility, a hallmark of spondylitis.
• FABER (Flexion, Abduction, External Rotation) Test (Patrick's Test): This test assesses the hip joint and the sacroiliac joint. The patient lies supine, and the examiner flexes one hip, abducts it, and externally rotates it, placing the ankle on the opposite knee (figure-4 position). Pressure is then applied to the knee and the opposite anterior superior iliac spine (ASIS). Pain in the SI joint suggests sacroiliitis.
• Gaenslen's Test: Used to provoke pain in the sacroiliac joint. The patient lies supine at the edge of the examination table. One leg is extended off the table, while the other hip is flexed towards the chest. Pressure is applied to the extended leg, causing hyperextension at the hip and potential SI joint strain.
• Chest Expansion Measurement: The circumference of the chest is measured at the nipple line (or fourth intercostal space) during maximal inspiration and maximal expiration. A difference of less than 2.5 cm (1 inch) can indicate restricted chest wall mobility due to costovertebral joint involvement, a common feature in advanced spondylitis.

Laboratory Tests

Blood tests are used to check for markers of inflammation and genetic predisposition, though they are not diagnostic on their own.

• Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP): These are non-specific markers of inflammation in the body. Elevated levels can indicate active inflammation, but they can also be raised in other conditions.
• HLA-B27 Genetic Marker: Approximately 90-95% of individuals with Ankylosing Spondylitis carry the HLA-B27 gene. While a strong association exists, possessing the gene does not mean an individual will develop AS, and conversely, some individuals with AS do not have the gene. It is a predisposing factor, not a diagnostic one.

Imaging Studies

Imaging techniques provide visual evidence of inflammation and structural changes in the spine and sacroiliac joints.

• X-rays: Conventional X-rays are often the initial imaging modality. They can reveal structural changes such as sacroiliitis (inflammation of the SI joints), which typically manifests as erosions, sclerosis (hardening of bone), and eventual fusion of the joints. In the spine, X-rays may show squaring of vertebrae, syndesmophytes (new bone formation leading to bridging between vertebrae), and ultimately, the characteristic "bamboo spine" appearance in advanced cases. However, X-ray changes may not be visible in the early stages of the disease.
• Magnetic Resonance Imaging (MRI): MRI is highly sensitive and can detect early inflammatory changes in the sacroiliac joints and spine that are not yet visible on X-rays. It can identify active inflammation (edema or bone marrow swelling) and subtle erosions or fatty changes, making it invaluable for early diagnosis and monitoring disease activity.

Interpreting the Results

The diagnosis of spondylitis is made by a healthcare professional, typically a rheumatologist, who integrates all the information gathered from the clinical assessment, blood tests, and imaging studies. No single "spondylitis test" provides a definitive answer. A combination of persistent inflammatory back pain, positive physical examination findings, elevated inflammatory markers, and characteristic changes on imaging, especially MRI of the sacroiliac joints, collectively points towards a diagnosis of spondylitis. The presence of the HLA-B27 gene can support the diagnosis but is not essential.

The Role of a Multidisciplinary Approach

Once diagnosed, the management of spondylitis involves a multidisciplinary approach, often including rheumatologists, physical therapists, and other specialists. Physical therapy and regular exercise are cornerstones of treatment, aiming to maintain spinal mobility, improve posture, reduce pain, and enhance overall functional capacity. Understanding the various "spondylitis tests" helps patients appreciate the comprehensive nature of their diagnosis and the rationale behind their treatment plan.