Background/Purpose: Autoantibodies to extractable nuclear antigens (ENA) are frequently ordered during the diagnostic workup of suspected autoimmune connective tissue diseases. There are no current guidelines for repeat test ordering. The objective of this study was to assess the utility of repeat ENA testing after an initial negative result.

Methods: This was a retrospective study conducted in a single, multicentre tertiary health network in Melbourne, Australia. Results of all ENA tests, performed using a Luminex bead assay, were extracted from the hospital laboratory information system. For patients who had a change in ENA result from negative to positive, clinical information was obtained from the hospital records regarding new diagnosis of an antinuclear antibody (ANA)-associated rheumatic disease (AARD).

Results: A total of 23,438 ENA tests were performed in 19,603 patients from 29th July 2013 to 28th September 2020. Most results 20,918 (89.2%) were negative with 215 (0.9%) being equivocal. Of the 2,305 positive tests, the most common ENA auto-antibody specificity detected was anti-Ro52 (1,185, 51.4%). 2,636 of 19,603 patients (13.4%) had more than one ENA test performed during the study period. Of these, most (2,523, 95.7%) had stable ENA results with no change compared to the first test. Only 53 patients (2.2%) had an ENA result that changed from negative to positive. Excluding patients with pre-existing rheumatic conditions and those under 18, there were five new AARD found in the remaining 34 patients.

Conclusion: ENA test results rarely change or result in a new diagnosis of an AARD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/utility-of-repeat-extractable-nuclear-antigen-antibody-testing-a-retrospective-audit/