Diagnostic Tests for Behçet's Disease
The diagnosis of Behçet's disease relies primarily on clinical criteria, as there are no specific laboratory tests that can definitively confirm the diagnosis. The most widely used diagnostic approach is the International Study Group (ISG) criteria, which requires the presence of recurrent oral ulceration plus any two of: genital ulceration, typical eye lesions, typical skin lesions, or a positive pathergy test 1.
Clinical Diagnostic Criteria
- Diagnosis requires recurrent oral aphthous ulcers plus at least two of the following: recurrent genital ulceration, uveitis/retinal vasculitis, or specific skin lesions 2, 1
- The International Study Group (ISG) criteria are the most widely used diagnostic criteria, though they have limitations including lack of major organ manifestations 3
- The International Criteria for Behçet's Disease (ICBD) 2014 criteria are more sensitive, especially in early disease, but may lead to overdiagnosis 3
Laboratory and Diagnostic Tests
HLA-B51 Testing
- HLA-B51 has moderate positive predictive value (approximately 55%) and high negative predictive value (84-90%) for Behçet's disease 4
- HLA-B51 testing should not be used as a standalone diagnostic test but rather as supportive evidence 4
- A negative HLA-B51 result can help exclude Behçet's disease, especially when clinical features are equivocal 4
Pathergy Test
- The pathergy test is the only diagnostic test included in the ISG criteria 3, 1
- The test involves observing for a papule or pustule formation 24-48 hours after sterile needle prick of the skin 5
- Positive results are more common in patients from Eastern Mediterranean and Asian countries than in Northern European or North American patients 5
Common Femoral Vein Thickness Measurement
- Recent studies show that common femoral vein thickness measurement can be a valuable diagnostic tool with sensitivity and specificity higher than 80% for a cut-off value of 0.5 mm 3
- This test needs further validation in different ethnic populations and disease groups 3
Monitoring Disease Activity
Clinical Activity Assessment
- The Behçet's Disease Current Activity Form has good interobserver reliability for assessing general disease activity 6
- This standardized form evaluates new clinical features present over the preceding 4 weeks 6
- It shows good agreement between physicians for rating oral and genital ulceration, skin involvement, arthritis, headache, and eye involvement 6
Laboratory Tests
- Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) can be used to monitor inflammatory activity, though they are not specific to Behçet's disease 7
- Complete blood count should be performed to check for anemia, leukocytosis, or thrombocytosis 7
Organ-Specific Evaluations
Ocular Involvement
- Regular ophthalmologic examinations are essential for patients with eye involvement 2
- Fluorescein angiography may be needed to detect retinal vasculitis 5
Vascular Involvement
- Vascular involvement occurs in approximately one-third of patients, affecting both arteries and veins 2
- Doppler ultrasound, CT angiography, or MR angiography may be needed to evaluate vascular manifestations 7
Neurological Involvement
- MRI with contrast is the imaging modality of choice for neuro-Behçet's 7
- CSF analysis may show pleocytosis and elevated protein levels 7
Gastrointestinal Involvement
- Endoscopy with biopsy is needed to evaluate gastrointestinal manifestations 8
- CT scan may show bowel wall thickening, particularly in the ileocecal region 8
Differential Diagnosis
- Differential diagnosis should exclude conditions such as Sweet's disease, pemphigus, erythema nodosum, and Crohn's disease 5
- In cases of neurological involvement, conditions like multiple sclerosis, neurosarcoidosis, and CNS vasculitis should be excluded 7
Monitoring Treatment Response
- Regular assessment of inflammatory markers to monitor disease activity is recommended 9
- Organ-specific monitoring is necessary based on the systems involved 9
- Non-compliance with treatment can lead to increased disease activity, organ damage, and reduced quality of life 9
Remember that Behçet's disease lacks pathognomonic laboratory findings, making the diagnosis primarily clinical after excluding other potential causes 3. The combination of clinical criteria, supportive laboratory tests, and appropriate imaging studies provides the most comprehensive approach to diagnosis and monitoring.