National Journal of Laboratory Medicine (Jul 2021)
An Overview of Various Diagnostic Methods to Detect Antinuclear Antibodies of Connective Tissue Diseases
Abstract
Antinuclear Antibodies (ANA) are present in many autoimmune disorders and these disorders are collectively called as Connective Tissue Diseases (CTD). There are various CTDs which include Systemic Lupus Erythematosus (SLE), Sjogren’s syndrome, Systemic Sclerosis (SS), Inflammatory Myositis (IM), Mixed Connective Tissue Disorder (MCTD) and Rheumatoid Arthritis (RA). Detection of ANAs in these CTDs is highly sensitive and is of utmost importance. The ANAs specific to SLE includes antidouble stranded Deoxyribonucleic Acid (antidsDNA), single stranded DNA (ssDNA). Scleroderma or Systemic Sclerosis (SS) is an immune mediated rheumatic disease where autoantibodies like topoisomerase 1, Ribonucleic Acid (RNA) polymerase 1 and fibrillarin are useful in diagnosis. Idiopathic Inflammatory Myositis (IIM) such as polymyositis and dermatomyositis are characterised by the presence of autoantibodies like PM-scl (Polymyositis-Scleromyositis), Mi-1 (Myositis specific autoantibody found in idiopathic inflammatory myositis), Mi-2 and Ku (DNA Binding Protein in dermatomyositis). Antibody titres against polypeptides on the U1 Ribonucleoprotein (U1RNP) is useful in the detection mixed CTD. Sjogren’s syndrome is characterised by the presence of serum autoantibodies against two ribonucleoproteinic complexes like Ro/SSA (Extractable nuclear antigen found in Sjogren's syndrome related antigen A auto antibodies) and La/SSB (Extractable nuclear antigen found in Sjogren's syndrome or lupus erythematous). ANA analysis can be done by techniques like indirect immunofluorescence method, Enzyme Linked Immuno Sorbent Assay (ELISA), Immunoprecipitation in agar and western blotting. All these diagnostic methods give precise identification of these antibodies with high accuracy. Farr assay, Multiplex Immunoassay (MIA), Flow cytometry, antigen microarray is also gaining importance in the diagnosis of ANAs. The objective of this study was to discuss various methods of ANA testing so that the clinicians know its relevance in diagnosis. Certain advancement in the diagnosis of ANA is also included in this review.
Keywords
