Comprehensive Workup for Ankylosing Spondylitis
The workup for ankylosing spondylitis should include patient history, clinical parameters, laboratory tests, and imaging according to the ASAS core set, with monitoring frequency determined by symptom severity and treatment regimen. 1
Clinical Assessment Components
History and Symptom Assessment
Inflammatory back pain characteristics:
- Morning stiffness lasting >30 minutes
- Pain improving with exercise but not with rest
- Awakening from sleep due to back pain (second half of night)
- Alternating buttock pain
Extra-articular manifestations:
- Acute anterior uveitis
- Inflammatory bowel disease
- Psoriasis
- Family history of spondyloarthritis
Physical Examination
Spinal mobility measurements:
- Modified Schober test
- Chest expansion
- Occiput-to-wall distance
- Lateral spinal flexion
- BASMI (Bath Ankylosing Spondylitis Metrology Index)
Peripheral joint and enthesis assessment:
- Count of swollen joints (44-joint assessment)
- Enthesitis examination (heel, greater trochanter, ischial tuberosity)
Laboratory Testing
Inflammatory markers:
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
Genetic testing:
- HLA-B27 (supportive but not diagnostic alone)
Imaging Studies
Sacroiliac joint imaging:
- Plain radiographs (anteroposterior view of pelvis)
- MRI of sacroiliac joints (if radiographs negative but clinical suspicion high)
Spine imaging:
- Lateral and anteroposterior views of lumbar spine
- Lateral view of cervical spine
- MRI of spine (for early inflammatory lesions)
Disease Activity Assessment
- Validated assessment tools:
- BASDAI (Bath Ankylosing Spondylitis Disease Activity Index)
- BASFI (Bath Ankylosing Spondylitis Functional Index)
- Patient global assessment (VAS)
- Pain assessment (VAS for spinal pain at night and overall)
- Morning stiffness duration
Additional Evaluations
Cardiovascular risk assessment:
- Blood pressure
- Lipid profile
- Blood glucose
Bone health assessment:
- DXA scan (especially in patients with syndesmophytes or spinal fusion)
Monitoring Recommendations
- Radiographic monitoring generally not needed more frequently than every 2 years 2
- More frequent monitoring may be necessary with significant changes in clinical status
- Regular assessment of disease activity using validated measures
Common Pitfalls to Avoid
- Relying solely on radiographs for early disease (MRI more sensitive for early sacroiliitis)
- Dismissing diagnosis due to negative HLA-B27 (10-15% of AS patients may be negative)
- Inadequate assessment of peripheral manifestations
- Overlooking extra-articular manifestations that may require specific management
- Failing to assess functional status and quality of life impact
The ASAS core set provides a standardized approach to assessment and should guide the comprehensive workup of patients with suspected or confirmed ankylosing spondylitis 2, 1. This structured approach ensures thorough evaluation of all disease domains and facilitates appropriate treatment decisions to improve outcomes related to morbidity, mortality, and quality of life.