What lab tests are used to assess Sjogren's (Sjogren's syndrome) activity?

Laboratory Tests for Assessing Sjögren's Syndrome Activity

The most important laboratory tests for assessing Sjögren's syndrome activity include anti-SSA/Ro and anti-SSB/La antibodies, antinuclear antibody (ANA), and rheumatoid factor (RF), which should be ordered as part of the initial evaluation of any patient with suspected Sjögren's syndrome. 1, 2, 3

Core Serological Tests

• Anti-SSA/Ro antibodies are the most sensitive serological marker for Sjögren's syndrome and score 3 points in the latest classification criteria, where a total score of ≥4 meets the criteria for primary Sjögren's syndrome 2
• Anti-SSB/La antibodies are less sensitive but highly specific when present, and should be included in the initial serological panel 1, 2
• Antinuclear antibody (ANA) testing by immunofluorescence is recommended as part of the standard evaluation 1, 3
• Rheumatoid factor (RF) testing should be included in the initial serological workup 1, 3

Additional Biomarkers

• Newer biomarkers that may be useful include antibodies to salivary protein 1 (SP1), carbonic anhydrase 6 (CA6), and parotid secretory protein (PSP), which may appear earlier in the disease course 1, 4
• These novel biomarkers can provide greater sensitivity and specificity than traditional biomarker testing alone, especially in early cases that may test negative for traditional markers 4
• C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) should be included to assess general inflammatory activity 1

Monitoring Disease Activity

• Decreased C4 levels at diagnosis indicate higher risk for lymphoma development (approximately 10% risk in Sjögren's patients) and should be monitored 2
• Repeat testing of serological markers after one year can be valuable, as most tests show high reliability (>80%) when repeated 5
• For patients with suspected pulmonary involvement, pulmonary function tests should be performed at baseline and followed at 3-6 month intervals for at least one year 1

Organ-Specific Assessment

Ocular Involvement

• Tear osmolarity testing using FDA-approved commercial devices can help confirm tear film instability 1
• Matrix metalloproteinase-9 testing can aid in diagnosis and assessment of dry eye disease activity 1
• Tear film break-up time and tear meniscus height assessment should be considered for objective evaluation of ocular surface disease 2, 3

Pulmonary Involvement

• High-resolution CT with expiratory views is recommended for patients with suspected interstitial lung disease 1
• Oximetry testing should be part of the initial evaluation for patients with suspected pulmonary involvement 1
• Pulmonary function tests including lung volumes, spirometry, diffusing capacity, and oxygen saturations at rest and with exercise should be performed 1

Clinical Pearls and Pitfalls

• Relying solely on a single measure of tear osmolarity can be misleading; correlation with clinical findings or differences in osmolarity over time is more informative 1
• False-negative results can occur with traditional biomarkers, especially in early disease, so newer biomarkers may be valuable in these cases 4, 6
• Hepatitis C-related sicca syndrome can be differentiated from Sjögren's syndrome by the absence of anti-SSA/SSB antibodies 2
• Discordance between pulmonary function test abnormalities, symptoms, and imaging findings can occur, so comprehensive evaluation is necessary 1
• Minor salivary gland biopsy remains an important diagnostic tool when serological testing is inconclusive, but incorrect biopsy methods can lead to false results 7

By systematically evaluating these laboratory parameters and correlating them with clinical findings, clinicians can more effectively assess Sjögren's syndrome activity and tailor management strategies accordingly.