{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T09:33:25Z","timestamp":1787045605010,"version":"build-2736575974"},"reference-count":24,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T00:00:00Z","timestamp":1787011200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004329","name":"Slovene Research and Innovation Agency","doi-asserted-by":"publisher","award":["P3-0314"],"award-info":[{"award-number":["P3-0314"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"name":"University Medical Center, Ljubljana","award":["TP 20250153"],"award-info":[{"award-number":["TP 20250153"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Background\/Objectives: Anti-double-stranded DNA antibodies (anti-dsDNA) are a specific biomarker for systemic lupus erythematosus (SLE). We aimed to analytically compare the in-house Farr fluorescence immunoassay (Farr-FIA), developed based on classical Farr-RIA, for the detection of anti-dsDNA with commercially available assays, including a chemiluminescence assay (CLIA) and the Crithidia luciliae immunofluorescence test (CLIFT). Additionally, we evaluated analytical agreement for diagnostic combinations of these methods. Methods: We analyzed 182 samples from patients at the Department of Rheumatology, UMC Ljubljana, using Farr-FIA, CLIFT (Immuno Concepts\u2014CLIFT 1 and Inova Diagnostics\u2014CLIFT 2), and the QUANTA Flash dsDNA CLIA on the BIO-FLASH analyzer (Inova Diagnostics). Agreement between methods and diagnostic combinations was assessed using Cohen\u2019s kappa. Results: Overall agreement between methods using manufacturer determined cut-offs ranged from 78.6% to 91.8% (\u03ba = 0.582\u20130.836). The in-house Farr-FIA showed 78.6\u201386.8% comparability with commercial assays (\u03ba = 0.582\u20130.730). Analytical agreement between combinations of two methods ranged from \u03ba = 0.788 to 1.000, indicating moderate to almost perfect agreement. Our routine combination of CLIFT 1 followed by Farr-FIA showed high agreement (\u03ba = 0.788\u20130.938) with other two-step approaches. Regardless of initial screening (CLIFT 1, CLIFT 2, or CLIA), applying Farr-FIA as a confirmatory method yielded highly consistent final classifications (97.3\u2013100% agreement). However, the screening methods differed in the proportion of samples requiring confirmatory method (e.g., CLIFT 2 identified more positives requiring Farr-FIA), consequently affecting workflow and costs, although the final diagnostic results remain the same. Conclusions: Farr-FIA demonstrated moderate to substantial analytical agreement with established commercial assays (CLIA and CLIFT). Several diagnostic combinations demonstrated high analytical agreement; however, the choice of initial screening method substantially influences the number of samples requiring confirmatory testing and, therefore, affects laboratory workload.<\/jats:p>","DOI":"10.3390\/diagnostics16162612","type":"journal-article","created":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T09:06:41Z","timestamp":1787044001000},"page":"2612","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Analytical Comparison of an In-House FARR Fluorescence Immunoassay with Commercial Analytical Assays for the Detection of Anti-Double-Stranded DNA Antibodies"],"prefix":"10.3390","volume":"16","author":[{"given":"Manca","family":"Ogri\u010d","sequence":"first","affiliation":[{"name":"Department of Rheumatology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sa\u0161a","family":"\u010cu\u010dnik","sequence":"additional","affiliation":[{"name":"Department of Rheumatology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia"},{"name":"Faculty of Pharmacy, University of Ljubljana, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katja","family":"Lakota","sequence":"additional","affiliation":[{"name":"Department of Rheumatology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia"},{"name":"The Faculty of Mathematics, Natural Sciences and Information Technologies (FAMNIT), University of Primorska, 6000 Koper, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"572","DOI":"10.3181\/00379727-96-23544","article-title":"A DNA-Reacting Factor in Serum of a Patient with Lupus Erythematosus Diffusus","volume":"96","author":"Ceppellini","year":"1957","journal-title":"Exp. 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