1.Autoantibody to Nuclear Antigen (ANA)
ANA can be positive in many rheumatic diseases, such as systemic lupus erythematosus, scleroderma, dry syndrome, rheumatoid arthritis, etc., and is therefore a screening antibody for the diagnosis of diffuse connective tissue disease. Healthy elderly people, infectious diseases and patients taking certain drugs (procainamide, hydrazinepyridazine, phenytoin sodium, isoniazid, etc.) can have positive ANA.
2.Anti-DNA antibodies
Anti-double-stranded DNA (dsDNA) antibodies have high specificity for the diagnosis of SLE, especially in patients with active SLE who have high titers of anti-dsDNA antibodies in the serum. Low titers of anti-dsDNA antibodies can also be found in many diseases and even in normal subjects.
3. Anti-ENA (Extractable Nuclear Antigen) antibodies
(1) Anti-nRNP (nuclear RNP): Anti-u1RNP antibody is almost always positive in mixed connective tissue diseases and its titer is high; in other connective tissue diseases, the positivity rate is low and the titer is low; it is a powerful indicator to distinguish connective tissue diseases from non-connective tissue diseases. Patients with positive anti-u1RNP antibodies often have swelling of the hands, Raynaud’s phenomenon, myositis, and sclerosis of the finger (toe) ends. It is thought that SLE patients with positive anti-u1RNP antibodies have a lower incidence of nephropathy if they are negative for anti-dsDNA antibodies; if they are present with anti-dsDNA and anti-Sm antibodies, there is a higher likelihood of lupus nephritis.
(2) Anti-Sm antibody: its positive rate is about 30% in SLE. Anti-Sm antibody is very helpful for retrospective diagnosis of early, atypical SLE or SLE in remission after treatment.
(3) Anti-SSA/RO antibody: This antibody is associated with dry syndrome (Sjogren syndromess), so it is named SSA.
(4) Anti-SSB/La, Ha antibody: another antibody related to dry syndrome is called SSB.
(5) Anti-rRNP antibody: For patients who have only positive rRNP antibody and negative ANA, they should be followed up closely and may develop into typical SLE after several years.
(6) Anti-Scl-70 antibodies: Patients with anti-Scl-70 positive SD have a more than 10-fold increased risk of developing interstitial lung degeneration compared to those with anti-Scl-70 negative SD. Anti-Scl-70 antibodies do not appear to be associated with cardiac or renal involvement.
(7) Anti-Jo-1 antibodies: In PM/DM patients with combined pulmonary interstitial degeneration, anti-Jo-1 antibodies are as high as 60%. rdquo;. Anti-Jo-1 antibody is often regarded as a marker antibody for PM/DM.
4.Rheumatoid Factor (RF)
It appears in many other diseases, such as autoimmune diseases: dry syndrome, SLE, PSS, PM/DM, etc.; infectious diseases: bacterial endocarditis, tuberculosis, leprosy, infectious hepatitis, schistosomiasis, etc.; non-infectious diseases: diffuse interstitial lung fibrosis, cirrhosis, slow-acting liver, nodular disease, macroglobulinemia, etc.
5.Anti-keratin antibody (AKA)
It is one of the indicators for early diagnosis and prognosis of RA. The positive rate of this antibody in the synovial fluid of patients is basically the same as that of serum, but the degree is significantly higher than the latter, suggesting that AKA may be synthesized locally in synovial fluid and play an important role in the formation of synovitis.
6, anti-cyclic citrullinated peptide (CCP) antibodies
Anti-CCP antibody positive RA disease is heavy, bone destruction is obvious.
7, anti-phospholipid antibodies (anti-phospholipid antibodies, APL)
The antiphospholipid antibodies (APL) are mainly associated with the antiphospholipid syndrome (APS). These include anticardiolipin antibody (ACL), lupus anticoagulant (LAC), anti-phosphatidylserine, anti-phosphatidylglycerol, anti-phosphatidylglycerol, anti-phosphatidic acid and anti-β2 –glycoprotein 1 (β2 – GP1), among others. These antibodies are commonly found in antiphospholipid syndrome (APS), SLE, neurological disorders, acute and chronic leukemia, renal and digestive disorders, and are closely associated with alterations in the coagulation system, thrombosis, and thrombocytopenia in these disorders, and are linked to the mechanisms of disease development. Currently, the only antiphospholipid antibodies routinely detected in clinical practice are anti-cardiolipin antibodies and lupus anticoagulant.
8.PR3-ANCA
The specificity of C-ANCA in diagnosing WG is more than 90%, plus PR3-ANCA can be more than 95%. Sensitivity depends on disease activity and stage of disease, with only 50% positivity in first-episode inactive WG, and almost 100% positivity in WG with typical activity. Although C-ANCA positivity has a high value in active WG, there is still a 25% chance of false positivity.PR3-ANCA is also detected in other primary vasculitis such as microscopic polyangiitis (MPA), necrotizing crescentic glomerulonephritis (NCGN), and polyarteritis nodosa (PAN).Another important clinical application of PR3-ANCA Another important clinical application of PR3-ANCA is that the antibody titer is consistent with disease activity and is often used as an indicator to judge the efficacy and estimate recurrence in patients with primary vasculitis such as WG, thus guiding clinical treatment.
9.MPO-ANCA
MPO-ANCA is mainly associated with MPA, NCGN, Churg-Strauss syndrome. MPO-ANCA is also seen in other diseases, such as PAN, anti-glomerular basement membrane disease (anti-GBM disease), WG, SLE, RA, pharmacological lupus, Felty syndrome, etc. MPO-ANCA is present in about 10%-15% of SLE MPO-ANCA is also associated with extra-articular damage and vascular damage in RA. MPO-ANCA is associated with disease activity and can also be used to determine MPO-ANCA correlates with disease activity and can also be used to determine efficacy, estimate relapse, and guide treatment.