30/07/2025
Autoimmunity special tests
Autoimmunity special tests are laboratory investigations used to detect autoimmune diseases by identifying autoantibodies, inflammatory markers, or specific immune cell responses. These tests help diagnose, monitor, and sometimes predict autoimmune conditions.
Here’s a categorized overview of the most common special tests for autoimmunity:
🧪 1. General Screening Tests
▪️ ANA (Antinuclear Antibody Test)
• Purpose: Screens for systemic autoimmune diseases.
• Positive in: SLE (lupus), Sjögren’s syndrome, scleroderma, mixed connective tissue disease.
▪️ RF (Rheumatoid Factor)
• Purpose: Detects antibodies associated with rheumatoid arthritis.
• Positive in: RA, Sjögren’s, and other conditions.
▪️ Anti-CCP (Cyclic Citrullinated Peptide Antibody)
• Purpose: More specific for rheumatoid arthritis.
• Helps distinguish RA from other arthritis causes.
🧪 2. Disease-Specific Autoantibodies
Disease Test(s) Notes
SLE (Systemic Lupus Erythematosus) Anti-dsDNA, Anti-Smith (Sm), ANA Anti-dsDNA correlates with disease activity.
Sjogren’s Syndrome Anti-SSA (Ro), Anti-SSB (La) Often ANA positive too.
Systemic Sclerosis (Scleroderma) Anti-Scl-70 (Topoisomerase I), Anti-centromere Subtype distinction.
Polymyositis/Dermatomyositis Anti-Jo-1, Anti-Mi-2 Muscle inflammation markers.
Autoimmune Hepatitis Anti-Smooth Muscle (SMA), Anti-LKM, ANA Liver enzymes also elevated.
Celiac Disease Anti-tTG (Tissue Transglutaminase), Anti-endomysial IgA deficiency must be ruled out.
Type 1 Diabetes Anti-GAD65, Anti-IA-2 Destruction of pancreatic β-cells.
Hashimoto’s Thyroiditis Anti-TPO (Thyroid Peroxidase), Anti-Tg Also in Graves’ disease.
🧪 3. Inflammatory and Complement Tests
• CRP (C-reactive protein): Nonspecific marker of inflammation.
• ESR (Erythrocyte Sedimentation Rate): Slower marker of inflammation.
• Complement C3 & C4: Often low in SLE during active disease.
🧪 4. HLA Typing (Genetic Susceptibility)
• HLA-B27: Associated with ankylosing spondylitis, reactive arthritis.
• HLA-DR3/DR4: Linked to Type 1 diabetes, lupus.
🧪 5. Others
• ANCA (Antineutrophil Cytoplasmic Antibodies): For vasculitis.
• c-ANCA: Granulomatosis with polyangiitis.
• p-ANCA: Microscopic polyangiitis, Churg-Strauss.
• Lupus Anticoagulant, Anticardiolipin, β2-glycoprotein I antibodies: For Antiphospholipid syndrome.
• Direct Coombs test: Autoimmune hemolytic anemia.