Newer approach of screening test for antinuclear antibodies: an enzyme-linked immunosorbent assay detecting antinuclear antibodies characteristic of connective tissue diseases

Abstract

An enzyme-linked immunosorbent assay (ELISA) has been developed for the detection of antinuclear antibodies (ANAs) previously established as diagnostic and/or prognostic marker ANAs for various connective tissue diseases. The antigen used in ELISA is a mixture of purified recombinant or natural antigens including single-and double-stranded DNA, RNP, Sm, SS-A/Ro, SS-B/La, centromere, topoisomerase I and Jo-1 antigens. Thirty hundred and fifty nine patients sera from a variety of connective tissue diseases and 113 normal human sera (NHS) were examined. ELISA ANAs were positive in 3.5% of NHS and 80.2% of patients sera at cut off index 11.5, whereas indirect immunofluorescent antinuclear antibodies (FANAs) using HEp-2 cells were positive in 9.7% of NHS and 92.5% of patients sera at 1:160 serum dilution. More than 80% of sera from systemic lupus erythematosus, mixed connective tissue disease and primary Sjögrens disease were ELISA ANAs positive. Mean value of ELISA ANAs was highest in sera of patients with MCTD. ELISA ANAs were positive in 92.5% of sera with marker ANAs for connective tissue diseases. Mean value of ELISA ANAs was higher in sera with more than two marker ANAs than in sera with a single ANA or in sera without marker ANAs. In contrast incidence and mean value of ELISA ANAs were low in sera positive for anti topoisomerase I antibody or anti Jo-1 antibody. Sensitivity, specificity and agreement (accuracy) for connective tissue diseases with marker ANAs were as follows: ELISA ANAs (at index 11.5): 92.5%, 88.3% and 90.9%: FANAs (at 1:160 serum dilution): 99.0%, 70.4% and 88.1%, respectively. ELISA ANAs, thus, are specific for connective tissue diseases when compared to FANAs and previous ELISA for the detection of total ANAs. Moreover, ELISA ANAs are able to measure precise ANAs titers and are much less labor intensive when screening a large number of clinical specimens.