Clinical diagnostic performance of different methods for the detection of antibodies to extractable nuclear antigens in connective tissue diseases: a cohort study.

Background: Different methods for anti-ENA identification have been used. This can lead to confusion regarding the interpretation of the test results in clinical practice. Some studies have reported differences in sensitivity and specificity, but few compare clinical outcomes. Based on that, our aim was to compare the performance characteristics of various methods commonly used to detect anti-ENA antibodies in the sera of patients suspected to have connective tissue diseases (CTDs).

Methods: 189 patients with orders for anti-ENA were analyzed. Three common methods were used: DID, ELISA, and HA. Sensitivity, specificity, PPV, NPV, and LR were calculated using CTDs as the reference standard.

Results: 69.3% of the patients had a CTD and 32.8% had SLE. Sensitivity and specificity, respectively, according to the technique were: ELISA (50.0% - 78.9%); DID (31.3% - 89.5%); HA (40.9% - 87.7%). PPV were: 88.5% (HA), 87.2% (DID) and 84.6% (ELISA), and NPV were: 40.5% (ELISA), 39.1% (HA) and 36.2% (DID).

Conclusions: Based on the very similar predictive test values, we believe that, at least in a moderate to high pretest probability, in our methodological scenario, there are no significant differences in the interpretation of test results when using ELISA, HA, and DID for anti-ENA detection.