Evaluation of diagnostic tests for antinuclear antibodies in rheumatological practice

To investigate and compare the accuracy and usefulness of diagnostic tests for antinuclear antibodies (ANA) a cross‐sectional study of sera derived from patients admitted to the Department of Rheumatology was tested for the presence of ANA using either indirect immunofluorescence on HEp‐2 cells, indirect immunoperoxidase techniques on HEp‐2 cells and mouse kidney, or two commercial enzyme‐linked immunosorbent assays (ELISA). The diagnostic sensitivity and predictive values of the tests were calculated and compared. The accuracy of tests was compared using receiver‐operating characteristics (ROC) methodology. All ANA‐positive sera were further analysed for the presence of antibodies against extractable nuclear antigens (anti‐ENA) and anti‐DNA. A moderate to good agreement was found between tests, with κ ranging from 0.469 to 0.659. Highest sensitivity for systemic lupus erythematosus (SLE; 93.3%) and primary Sjögren's syndrome (SS; 70%) was found using immunofluorescence on HEp‐2 cells. Immunofluorescence on HEp‐2 cells performed statistically better than the other tests in predicting SLE but not SS. All tests except mouse kidney showed good and comparable performance in detecting sera with anti‐ENA and anti‐DNA. At the given cut‐off values indirect immunofluorescence on HEp‐2 cells performed best. All assays except mouse kidney showed performance characteristics sufficient for use in routine analysis of ANA.