[Performance and clinical evaluation of antinuclear antibody test based on fluorescence enzyme immunoassay]

The measurement of antinuclear antibodies (ANA) is used for screening of connective tissue diseases (CTD) in the laboratory. ANA detection is performed by indirect immunofluorescence (IF) assay on HEp-2 cells from human larynx carcinoma. However, it lacks specificity for the identification of specific diseases and antigen reactivity. The aim of the present study was to evaluate the EliA CTD Screen (EliA), a new enzyme fluoroimmunoassay (Phadia AB, Uppsala, Sweden) for detection of ANA in human serum.

The study involved a total of 732 serum samples, 200 from healthy donors, 297 from patients with CTD and 235 from patients with rheumatoid arthritis, vasculitis syndrome and relative disease of CTD. For all sera, ANA was measured by IF, commercial assay (MESACUP) and EliA.

The sensitivity and specificity of EliA were 73.7% and 78.7%, respectively, whereas those of MESACUP were 80.8% and 64.7%, respectively. Area under the receiver operating curves for EliA, MESACUP and IF were 0.821, 0.786 and 0.730, respectively. The concordance rate between EliA and MESACUP was 84.2%. These discrepancies between those 2 assays were found in 84 sera. Further investigation were done by each ANA antigen tests for the discrepant results of EliA in 83 sera. The discrepancies might be occurred by antigen difference or non-specific response.

AUC results showed that the diagnostic performance of EliA was superior to MESACUP and IF. EliA had a good performance as method for screening of CTD.