Screening for Smith antibodies is used in the investigation of patients with connective tissue autoimmune symptoms and signs and in whom anti-nuclear antibodies (ANAs) are positive.
Antibodies against Extractable Nuclear Antigen (ENA) or anti-ENA are used to diagnose systemic lupus erythematosus (SLE) and mixed connective tissue disease and to exclude other autoimmune diseases. Anti-ENAs are a type of antinuclear antibody against certain core antigens consisting of RNA and proteins. The most common ENA antigens are Smith (SM) and ribonucleoprotein (RNP). The ENA antigens also include SS-A (Ro), SS-B (La), Jo-1, and Scl-70.
Antinuclear Smith (anti-Smith, anti-SM) are found in about 30% of patients with systemic lupus erythematosus and in about 8% of patients with mixed connective tissue disease. However, they are not found in patients with other collagen diseases.
Antinuclear antibodies against ribonucleoprotein (anti-RNP) are found in approximately 100% of patients with mixed connective tissue disease and in approximately 25% of patients with systemic lupus erythematosus, discoid lupus, and progressive systemic sclerosis (scleroderma). High anti-RNP titers indicate mixed connective tissue disease.
Antibodies against histidyl tRNA synthetase (Anti-Jo-1) are found in patients with autoimmune interstitial pulmonary fibrosis and in a few patients with autoimmune myositis.
Anti-SS-A (Ro) and anti-SS-B (La) antibodies are mainly used in the diagnostic evaluation of Sjögren's syndrome.
Scleroderma antibodies (anti-Scl-70) are found in patients with scleroderma and CREST syndrome.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.