Hep-2000 indirect immunofluorescence assay - An emerging screening tool for detection of antinuclear autoantibodies in various connective tissue disorders.

Background: Connective tissue disorders (CTD's) are a group of autoimmune disorders having multifactorial etiology, multisystem involvement and overlapping clinical features. Their prevalence has been increasing in India, with Systemic lupus erythematosus (SLE) being the most common CTD, affecting mostly females. Antinuclear Antibodies (ANA) directed against a variety of nuclear antigens detectable in the serum are used for screening, diagnoses, and monitoring of autoimmune diseases, with immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA) being the most widely used methods.

Aims: 1.To evaluate the diagnostic significance of IFA in screening of Autoimmune CTDs. 2.To study different titres and patterns shown by ANA positive samples.

Materials And Methods: For IFA, patient's sera is incubated with substrate cells, and bound antibodies are detected by incubation with a dye-conjugated anti-human immunoglobulin which are visualized by fluorescent microscopy and different ANA titres and patterns were analysed.

Results: 57 samples were examined for ANA by Indirect IFA, of which 21 (36.8%) were ANA positive with a female preponderance (71.9%) in the peri-menopausal age group. Most common pattern reported was Speckled followed by Homogenous. The sensitivity & specificity of IIFA was found to be comparable with ELISA.

Conclusion: CTD's are a group of autoimmune disorders with a plethora of clinical presentations, necessitating the need of a more specific and accurate screening test. ANA by IIFA gives patterns, which are associated with specific antibodies that help in reaching a diagnosis. ANA testing is a cost effective and non-invasive technique that can be used as a reliable screening test for Autoimmune disorders.