Comparative Study of Immunofluorescent Antinuclear Antibody Test and Line Immunoassay Detecting 15 Specific Autoantibodies in Patients With Systemic Rheumatic Disease

Based on the currently proposed algorithms, antibodies specificities (sp-ANAs) are identified mainly in samples positive for fluorescent antinuclear antibodies (FANA) screening tests. The purpose of the present study was to compare diagnostic performances of FANA and line immune assay (LIA) detecting 15 sp-ANAs in patients with systemic rheumatic diseases (SRD). In 948 sera from the patients with SRD (n = 590) and non-SRD (n = 358), we evaluated the fluorescent patterns and intensities in the FANA test, and compared the FANA results with sp-ANAs against nRNP, Sm, SS-A, Ro52, SS-B, Scl-70, PM/Scl, Jo-1, CENP B, PCNA, dsDNA, nucleosome, histone, ribosomal-P, and M2. The sensitivity and specificity was 75.9% and 52.5% of FANA test and 62.0% and 84.4% of sp-ANAs test for SRD detection. The overall agreement between FANA and sp-ANAs results was 69.2% (Kappa coefficient; 0.404). According to the clinical diagnosis, the levels of agreement varied from 33.3% to 83.1%. The positive predictive values of each FANA pattern for the detection of sp-ANAs were less than 50% except for the discrete speckled pattern (91.7%). The 1:100 intensity of FANA as well as the monoreactivity of LIA, anti-SSA(-)/anti-Ro52(+), or FANA(-)/sp-ANAs(+) was associated with non-SRD. Antibodies against ribosomal-P or PCNA were specific for systemic lupus eryhthematosus. This study highlights the need for careful interpretation of FANA test results to assess sp-ANAs and the application of sp-ANAs tests including less-common autoantibodies. In patients with clinical suspicion of SRD, screening with both FANA and sp-ANAs tests could improve diagnostic efficiency.