Immunity status, individual response to disease and types of antibodies produced are well known to vary from person to person, place to place and probably from population to population. A broad spectrum of specific auto antibodies that have so far been associated with specific rheumatic diseases, as noted in Western literature, has been well taken as a reference standard all over the world. There is neither research work nor any data correlating the auto antibodies and their antinuclear antibody (ANA) patterns with the immunoprofile in the Indian population to date.
To understand a definite association between ANA patterns and specific antibodies in the serum in the Indian study population and to document similarities / differences with the West.
This prospective and retrospective double blind study was undertaken on the South Indian population referred for ANA testing by Indirect Immunofluorescence method and by immunoline methods.
Serum samples of patients from a random South Indian population who sought medical help for rheumatic disease were subjected for ANA testing by indirect immunofluorescence (IIF) method and line immunoassay during the study period of 27 months. Serum samples were processed in dilution of 1:100 using HEp - 2010 / liver biochip (Monkey) (EUROIMMUN AG). The serum samples which were further processed for line immunoassay were treated in 1:100 dilution on nylon strips coated with recombinant and purified antigens as discrete lines with plastic backing (EUROIMMUN AG) coated with antigens nRNP / Sm, Sm, SSA, Ro-52, SSB, Scl-70, PM-Scl, PCNA, Jo-1, CENP-B, dsDNA, nucleosomes, histones, ribosomal protein-P, anti-mitochondrial antibodies (AMA-M2) along with a control band. The analysis was done by comparing the intensity of the reaction with positive control line by image analysis.
The antinuclear antibody indirect immunofluorescence (ANA - IIF) patterns obtained were projectable to visualize a certain spectrum of specific antibodies such as homogenous (45.5%) with dsDNA, nucleosomes, histones, SSA / Ro-52, RIB and RNP / Sm, speckled pattern (35.6%) with Sm, RNP, SSA/Ro-52, SSB, Sm and RIB; nucleolar pattern with Scl-70, Sm, RNP and centromere pattern with CENP-B. The methodology indicated that, cytoplasmic pattern noted in ANA also needs to be correlated with primate liver in a biochip, which should prompt further decision for a request for line immunoassay and it is preferable for two pathologists to report independently and sign out a consensus ANA report for better predictive value.
As a definite correlation between the ANA patterns and the group of antibodies was detected by line immunoassay, one could predict presence of certain specific auto antibodies for a particular ANA pattern identified. This may restrict one from requesting for line immunoassay, which is expensive and economizes on the cost of laboratory investigations in a developing country like India. Thus, screening of sera by ANA-IIF method alone may suffice and probably reduce the expense of detailed immunological work-up with minimal loss in diagnostic accuracy. This study, the first of its kind in India, provides database and reference for the Indian subpopulation.