Immunofluorescence--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 (IF-ANA). COBAS-ANA and MBL-ANA were used, in the former a mixture of antigens extracted from HEp-2 cells and multiple recombinant antigens was immobilized on beads as the antigen, and in the latter 9 kinds of purified or recombinant proteins are immobilized on 96-well plates. We first compared an ability to differentiate 258 connective tissue disease (CTD) patients (except rheumatoid arthritis) from 257 healthy subjects between COBAS-ANA and IF-ANA. The sensitivity and specificity of COBAS-ANA were 84% and 94%, respectively, while those of IF-ANA at a cutoff dilution of 1:160 were 81% and 87%. The receiver operating characteristic (ROC) analysis showed a significant 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. Among the 1123 subjects, a total of 145 disease-specific ANAs were detected in 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 detecting disease-specific ANAs and screening CTD patients. We believe that EIA-ANA should be the 'gold standard' especially for screening a large number of samples, although there is some room for technical improvement.
Kumagai
S
S
Department of Clinical and Laboratory Medicine, Kobe University School of Medicine, Hyogo, Japan. kumagais@kobe-u.ac.jp
Hayashi
N
N
D000974:Antibodies, Antinuclear / Q000032:analysis*; D016022:Case-Control Studies; D003240:Connective Tissue Diseases / Q000175:diagnosis* / Q000276:immunology*; D003625:Data Collection; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods / Q000706:statistics & numerical data; D007564:Japan; D008297:Male; D008403:Mass Screening; D012680:Sensitivity and Specificity
D000974:Antibodies, Antinuclear