Diagnostic Accuracy Of The Fidis Multiplex Fluorescent Microsphere Immunodetection System For Anti-Extractable Nuclear Antigen (Ena) Antibodies In Connective Tissue Diseases

Background: Anti-extractable nuclear antigen antibodies (ENA) are markers of connective tissue diseases (CTDs).Methods: We compared FIDIS reagents in the multiplex fluorescent microsphere immunodetection system to INNO-LIA and immunodiffusion for 174 antinuclear antibody-positive patients, 102 with well-defined CTDs and 72 disease controls.Results: No significant differences were found in sensitivity or specificity between FIDIS and immunodiffusion, or between FIDIS and INNO-LIA for all anti-ENA in all CTD patients; nor were any differences found for individual anti-ENAs within distinct CTDs. The FIDIS sensitivity was 41% (anti-SSA) and 17% (anti-SSB) in lupus erythematosus (LE) or primary Sjogren's syndrome; 5% (anti-ribosome and anti-Sm) in LE; 17% (anti-RNP) in LE or mixed CTD; 21% (anti-Sc170) in systemic sclerosis; and 61% (anti-centromere) in limited systemic sclerosis. The specificity reached 88%-100%. Receiver operating characteristic curve areas did not differ between FIDIS and INNO-LIA. Agreement ranged from 91% (anti-SSB) to 99% (anti-Jo1) between FIDIS and INNO-LIA, and from 95% (anti-Sc170) to 100% (anti-Sm) between FIDIS and immunodiffusion. Samples scored positive with all techniques in 83% (anti-centromere), 70% (anti-RNP), 67% (anti-Jo1), 60% (anti-SSA), 40% (anti-SSB), 33% (anti-ribosome), 25% (anti-Sm) and 13% (anti-Sc170) of cases.Conclusions: The diagnostic performance of FIDIS anti-ENA reagents is comparable to immunodiffusion and INNO-LIA.