Blood Work for Suspected Sjögren's Syndrome
For suspected Sjögren's syndrome, the essential blood work should include anti-SSA/Ro antibodies, anti-SSB/La antibodies, antinuclear antibodies (ANA), and rheumatoid factor (RF), as these are the core serological tests recommended by the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) for diagnosis. 1
Core Serological Testing
- Anti-SSA/Ro antibodies - Most important serological marker, weighted heavily (3 points) in diagnostic criteria 1
- Anti-SSB/La antibodies - Common in Sjögren's syndrome 1, 2
- Antinuclear antibodies (ANA) - Important screening test 1, 3
- Rheumatoid factor (RF) - Often positive in Sjögren's syndrome 1, 3
Additional Laboratory Tests
- Complete blood count (CBC) - To assess for cytopenias that may occur with Sjögren's
- Inflammatory markers:
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
- Immunoglobulin levels - To evaluate for hypergammaglobulinemia
- Complement levels (C3, C4) - May be decreased in active disease
Important Considerations
- Up to 18% of Sjögren's patients may be seronegative for traditional antibodies, potentially leading to delayed or missed diagnosis 4
- Anti-SSA/Ro antibodies are the most sensitive serological marker and carry the highest weight (3 points) in the ACR/EULAR classification criteria 1
- The presence of these antibodies has been associated with earlier disease onset, greater glandular dysfunction, and more extraglandular manifestations 2
Emerging Biomarkers
Consider these additional antibodies in cases where clinical suspicion is high but traditional antibodies are negative:
- Anti-AQP5, anti-SP-1, anti-CA6, and anti-PSP antibodies show promise as additional diagnostic markers 4
Diagnostic Context
Remember that serological testing is just one component of the ACR/EULAR classification criteria for Sjögren's syndrome. A total score ≥4 is required for diagnosis based on the following weighted criteria 1:
| Criterion | Weight |
|---|---|
| Anti-SSA/Ro antibody positivity | 3 |
| Focal lymphocytic sialadenitis on labial salivary gland biopsy | 3 |
| Abnormal ocular staining score | 1 |
| Schirmer test ≤5 mm/5 minutes | 1 |
| Unstimulated salivary flow rate ≤0.1 ml/minute | 1 |
Clinical Pitfalls to Avoid
- Don't rely solely on serology for diagnosis; negative antibodies don't exclude Sjögren's syndrome
- Different testing methods (ELISA, immunofluorescence) may yield varying results 5
- Consider organ-specific presentations of Sjögren's syndrome that may present before sicca symptoms develop ("occult" Sjögren's) 6
- Always interpret results in the context of clinical findings and other diagnostic tests
When clinical suspicion is high despite negative initial serology, consider referral to rheumatology for further evaluation, including potential labial salivary gland biopsy.