{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,28]],"date-time":"2026-07-28T18:58:43Z","timestamp":1785265123472,"version":"3.55.0"},"reference-count":43,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T00:00:00Z","timestamp":1772755200000},"content-version":"unspecified","delay-in-days":64,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["Lupus Sci Med"],"accepted":{"date-parts":[[2026,2,7]]},"published-print":{"date-parts":[[2026,1]]},"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>Despite the reported clinical significance of anti-C1q immunoglobulin G autoantibodies (anti-C1q) for SLE and the development of anti-C1q commercial kits, their performance characteristics in routine patient evaluation remain poorly defined.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In this cross-sectional study, an unselected cohort of 107 patients with suspicion of a systemic autoimmune disease and 102 controls were included and evaluated for anti-C1q autoantibodies with three kits (B\u00fchlmann, Orgentec and Werfen). Patients in the unselected cohort were classified as having SLE or a mimicker condition. Disease activity was assessed using Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)-2K and SLE patients were subclassified based on the presence of lupus nephritis (LN) (history\/active). Each kit was assessed for diagnostic performance. The degree of association between anti-C1q and SLEDAI\/complement levels was assessed using the Spearman correlation coefficient (rho). Between-kit agreement was evaluated using Fleiss \u0198.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Werfen had the best performance in discriminating patients with SLE from non-SLE (area under the curve (AUC)=0.76), whereas for the SLE versus mimicker comparison B\u00fchlmann (AUC=0.71) and Werfen (AUC=0.71) exhibited adequate discrimination. Among patients with SLE, all kits exhibited poor discrimination of patients with history of LN versus non-renal SLE, but Orgentec displayed good discrimination for patients with active LN from non-active LN (AUC=0.74). A positive correlation was observed between anti-C1q and SLEDAI scores, whereas a negative correlation was found between anti-C1q and complement C3 and C4 across all kits. Agreement for SLE between the three kits was moderate (\u0198=0.42).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Anti-C1q can identify patients with SLE and correlate with global and renal disease activity, highlighting their potential to function as follow-up markers in SLE. Agreement with commercial anti-C1q kits is variable. Further studies are required to harmonise anti-C1q kits for optimal routine patient evaluation.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/lupus-2025-001896","type":"journal-article","created":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T14:35:22Z","timestamp":1772807722000},"page":"e001896","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Clinical utility and performance of anti-C1q antibodies for SLE: comparative analysis of three different assays"],"prefix":"10.1136","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2957-9760","authenticated-orcid":false,"given":"Mariana","family":"Gonzalez-Trevi\u00f1o","sequence":"first","affiliation":[{"name":"Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA"},{"name":"Division of Rheumatology, Mayo Clinic, Rochester, Minnesota, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"MeLea 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