Immunofluorscense - still the 'gold standard' in ANA testing?

A usefulness of enzyme immunoassay (EIA)-based antinuclear antibodies (ANA) tests was evaluated in comparison with the immunofluorescence ANA assay (I F-ANA). COBAS-ANA and MBL-ANA were used, in the former a mixture of antigen s extracted from HEp-2 cells and multiple recombinant antigens was immobili zed on beads as the antigen, and in the latter 9 kinds of purified or recom binant proteins are immobilizedon 96-well plates. We first compared an abil ity to differentiate 258 connective tissue disease (CTD) patients (except r heumatoid arthritis) from 257 healthy subjects between COBAS-ANA and IF-ANA . The sensitivity and specificity of COBAS-ANA were 84 % and 94 %, respecti vely, while those of IF-ANA at a cutoff dilution of 1: 160 were 81 % and 87 %. The receiver operating characteristic (ROC) analysis showed a significa nt superiority of COBAS-ANA to IF-ANA. Moreover, when the cutoff index was set at 0.6, the COBAS-ANA could detect the 8 disease-specific ANAs as well as IF-ANA at a cutoff dilution of 1:40. A possible availability of MBL-ANA in a periodic health examination in certain towns was also demonstrated. Am ong the 1123 subjects, a total of 145 disease-specific ANAs were detected i n 126 subjects. MBL-ANA could catch disease-specific ANAs with almost same efficacy of IF-ANA. Annual survey of the residents by MBL-ANA may lead to a detection of CTD patients. EIA-based ANA tests are very useful for both de tecting disease-specific ANAs and screening CTD patients. We believe that E IA-ANA should be the 'gold standard especially for screening a large number of samples, although there is some room for technical improvement.