What is TRUE about antinuclear antibody (ANA) -
High-Yield Explanation
Ans. is 'b i.e., Double stranded Anti-DNA is specific for SLE "Antibodies to double - stranded DNA and the Smith (Sm) antigen are viually diagnostic of SLE". -- Robbins Antibodies in SLE SLE is an autoimmune disease and the fundamental defect is a failure of mechanism that mantain self tolerance. o Failure of tolerance results in formation of autoantibodies and autoimmunity. o Amongst these antibodies, most impoant are antinuclear antibodies (ANA). ANAs are directed against several nuclear antigens and can be of following types. 1. Generic antinuclear antibody o Most common (between 95 to 100% of the patients). o Against DNA, RNA and proteins. o Most sensitive antibodies for SLE --> best screening test. o But, not specific because patients with other autoimmune diseases also show positive test. 2. Anti ds DNA antibody o Most specific for SLE o Not sensitive 3. Anti Smith (Sm) antibody o Along with anti ds DNA antibody, most specific for SLE. o Not sensitive 4. Antihistone antibody Paicularly seen in drug induced SLE. 5. Anti RNP- SS - A (Ro), SS-B (La) Seen in neonatal lupus with congenital hea block and in subacute cutaneous lupus. o Associated with decreased risk of lupus nephritis. o More common in sjogren syndrome (Sicca syndrome). 6. Anti Ui RNP Seen in patients that have overlap feature of several rheumatic syndromes including SLE Mixed connective tissue disease. 7. Anti DNA topoisonerase (Scl - 70) o In less than 5% of patients of SLE. o More common in patients with systemic sclerosis. 8. Anticentromere In less than 5% of patients of SLE. More common in patiens with localized form of systemic sclerosis, i.e. scleroderma. 9. Anti-histidyl t-RNA systhatase In less than 5% of SLE patiens. o More common in patiens with inflammatory myopathies. Besides antinuclear antibodies following antibodies are also seen in SLE ? 1. Antiphospholipid (lupus anticoagulant) 2. Antierythrocyte ---> causes hemolytic anemia 3. Antiplatelet --> Causes thrombocytopenia 4. Antiribosomal P 5. Antineuronal