Sjögren’s Syndrome (SS) is a chronic autoimmune disease where the immune system attacks the body’s tissues, primarily targeting the glands that produce tears and saliva. This leads to the common symptoms of dry eyes and dry mouth. Since SS is systemic, it can affect organs throughout the body. Because symptoms can be vague or mimic other conditions, laboratory tests are crucial for confirming the diagnosis, differentiating it from similar illnesses, and monitoring disease activity. These blood tests provide objective evidence of underlying immune system dysfunction by looking for specific proteins and signs of inflammation.
Specific Autoantibodies Confirming Diagnosis
The most direct laboratory findings for Sjögren’s Syndrome are autoantibodies—proteins created by the immune system that target the body’s healthy cells. These markers are tested in a blood sample to establish the condition’s autoimmune nature.
The Antinuclear Antibody (ANA) test is often the first screen performed. A positive result is common in Sjögren’s patients, frequently showing a “speckled” pattern. However, a positive ANA alone is not definitive, as this marker is found in other autoimmune diseases and some healthy individuals.
The presence of two specific autoantibodies, Anti-Ro/SSA and Anti-La/SSB, provides a much stronger indication of SS. Anti-Ro/SSA antibodies are found in 60% to 80% of patients and are a significant component of the diagnostic criteria. These antibodies target specific RNA-protein complexes within the cell nucleus.
Anti-La/SSB antibodies are detected less frequently, appearing in about 30% to 50% of patients. They are almost always found when Anti-Ro/SSA is also present. When both are positive, the diagnosis is significantly strengthened and may indicate potential complications.
Another common finding is the presence of Rheumatoid Factor (RF). Although primarily associated with Rheumatoid Arthritis, RF is positive in 60% to 70% of Sjögren’s patients, highlighting the overlap between these conditions.
Indicators of Systemic Inflammation and Immune Overactivity
Other laboratory tests measure the general level of systemic inflammation and immune system overactivity to monitor the disease’s overall impact.
An elevated Erythrocyte Sedimentation Rate (ESR) is a non-specific test where a high rate suggests inflammation is present. This increased rate is often caused by high levels of immune proteins, or immunoglobulins, which cause red blood cells to clump and settle faster.
C-Reactive Protein (CRP) is another marker frequently checked. It is a protein produced by the liver in response to acute inflammation. While elevated CRP signals inflammation, it is often not as dramatically raised in Sjögren’s Syndrome as in other inflammatory conditions.
Both ESR and CRP are useful for tracking systemic activity, but they do not always correlate directly with the severity of glandular symptoms.
A common abnormality is hypergammaglobulinemia, which refers to elevated levels of gamma globulins, the group of proteins that includes most antibodies. This finding reflects the overproduction of antibodies by the activated immune system, a hallmark of the autoimmune process.
Labs Monitoring for Organ Involvement and Secondary Effects
Since Sjögren’s Syndrome is systemic, laboratory monitoring includes tests for potential involvement of major organs and secondary effects on blood health.
A Complete Blood Count (CBC) is a standard test that can reveal abnormalities. Mild anemia, often resulting from chronic inflammation, is documented in up to 34% of patients. Leukopenia, a low white blood cell count, is also frequent, occurring in 15% to 60% of patients, typically due to a decrease in lymphocytes or neutrophils.
Kidney and Liver function tests are routinely performed to detect organ impairment. Sjögren’s can cause inflammation in the kidneys, known as interstitial nephritis, which may be indicated by protein in the urine or a low serum bicarbonate level.
Elevated liver enzymes can signal liver involvement, such as primary biliary cholangitis, which is associated with SS.