{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T02:44:42Z","timestamp":1790649882899,"version":"4.1.0"},"reference-count":37,"publisher":"BMJ","issue":"3","license":[{"start":{"date-parts":[[2025,9,23]],"date-time":"2025-09-23T00:00:00Z","timestamp":1758585600000},"content-version":"unspecified","delay-in-days":84,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"name":"GRAPPA","award":["educational grant"],"award-info":[{"award-number":["educational grant"]}]},{"DOI":"10.13039\/100013322","name":"EFPIA","doi-asserted-by":"crossref","id":[{"id":"10.13039\/100013322","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100010767","name":"Innovative Medicines Initiative","doi-asserted-by":"publisher","award":["101007757"],"award-info":[{"award-number":["101007757"]}],"id":[{"id":"10.13039\/501100010767","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Partners fellowship program","award":["www.partner-fellows.de"],"award-info":[{"award-number":["www.partner-fellows.de"]}]},{"DOI":"10.13039\/100004312","name":"Eli Lilly and Company","doi-asserted-by":"publisher","award":["translational research grant"],"award-info":[{"award-number":["translational research grant"]}],"id":[{"id":"10.13039\/100004312","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["RMD Open"],"accepted":{"date-parts":[[2025,8,4]]},"published-print":{"date-parts":[[2025,7]]},"abstract":"<jats:sec>\n                  <jats:title>Objectives<\/jats:title>\n                  <jats:p>C reactive protein (CRP) is frequently normal in psoriatic arthritis (PsA) despite active disease, complicating inflammation assessment. This study aimed to evaluate alternative biomarkers of inflammation in early PsA.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>Adult patients with early, treatment-na\u00efve PsA were enrolled in the prospective multicentre cohort and compared with early rheumatoid arthritis (RA) and healthy controls (HCs). Clinical assessments, inflammatory markers and peripheral blood counts were collected. For this study, baseline and 1-year data were used. Serum complement factor 3 (C3), calprotectin (S100A8\/9) and serum amyloid A (SAA) were measured by ELISA. Discriminatory performance was evaluated using receiver operating characteristic curve analysis.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>A total of 67 PsA, 50 RA patients and 61 HC were included. At baseline, median levels of C3 (1.38\u2009g\/L) and S100A8\/9 (5.58 \u00b5g\/mL) were significantly elevated in PsA compared with HC and were comparable to RA. In the \u2018CRP-negative\u2019 subgroup, C3 and S100A8\/9 were increased in PsA as compared with HC. In the obese subgroup, CRP levels did not discriminate PsA, RA and HC. However, S100A8\/9 was significantly increased in PsA and RA as compared with HC, whereas SAA and derived inflammatory ratios (neutrophil\/monocyte ratio, lymphocyte\/monocyte ratio) did not discriminate PsA, RA or HC. After 1 year, C3 and S100A8\/9 decreased significantly in PsA patients achieving low disease activity. In the obese subgroup, the composite marker C3\u00d7calprotectin demonstrated superior diagnostic performance as compared with CRP (area under the curve=0.836).<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>C3 and calprotectin are elevated in early PsA and are responsive to treatment. These markers outperform CRP in obese and CRP-negative patients and may support improved diagnosis and disease monitoring in clinical practice.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1136\/rmdopen-2025-006019","type":"journal-article","created":{"date-parts":[[2025,9,24]],"date-time":"2025-09-24T05:20:17Z","timestamp":1758691217000},"page":"e006019","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":5,"title":["Serum calprotectin and complement factor C3 are superior biomarkers of inflammation in early psoriatic arthritis as compared with C-reactive protein"],"prefix":"10.1136","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9190-7369","authenticated-orcid":false,"given":"Alla","family":"Ishchenko","sequence":"first","affiliation":[{"name":"Rheumatology, UZ Leuven, Leuven, Belgium"},{"name":"Rheumatology, Ziekenhuis aan de Stroom, Antwerpen, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Margot","family":"Van Mechelen","sequence":"additional","affiliation":[{"name":"Department of Immunology, Allergology and Rheumatology, University of Antwerp, Antwerpen, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8579-6914","authenticated-orcid":false,"given":"Sofia","family":"Pazmino","sequence":"additional","affiliation":[{"name":"Department of Clinical and Experimental Endocrinology, KU Leuven, Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lies","family":"Storms","sequence":"additional","affiliation":[{"name":"Skeletal Biology and Engineering Research Centre,Department of Development and Regeneration, KU Leuven, Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Barbara","family":"Neerinckx","sequence":"additional","affiliation":[{"name":"Rheumatology, UZ Leuven, Leuven, Belgium"},{"name":"Skeletal Biology and Engineering Research Centre,Department of Development and Regeneration, KU Leuven, Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0340-3580","authenticated-orcid":false,"given":"Patrick","family":"Verschueren","sequence":"additional","affiliation":[{"name":"Rheumatology, UZ Leuven, Leuven, Belgium"},{"name":"Skeletal Biology and Engineering Research Centre,Department of Development and Regeneration, KU Leuven, Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rik","family":"Lories","sequence":"additional","affiliation":[{"name":"Rheumatology, UZ Leuven, Leuven, Belgium"},{"name":"Skeletal Biology and Engineering Research Centre,Department of Development and Regeneration, KU Leuven, Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3848-5122","authenticated-orcid":false,"given":"Kurt","family":"de Vlam","sequence":"additional","affiliation":[{"name":"Rheumatology, UZ Leuven, Leuven, Belgium"},{"name":"Skeletal Biology and Engineering Research Centre,Department of Development and Regeneration, KU Leuven, Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2025,9,23]]},"reference":[{"key":"2025092322201201000_11.3.e006019.1","unstructured":"Lindqvist UR , Alenius GM , Husmark T , et al . Psoriatic Arthritis Group of the Society for Rheumatology. The Swedish early psoriatic arthritis register-- 2-year followup: a comparison with early rheumatoid arthritis. J Rheumatol 2008;18278834."},{"key":"2025092322201201000_11.3.e006019.2","first-page":"413","article-title":"Interleukin-6 and soluble interleukin-2-receptor in psoriatic arthritis: correlations with clinical and laboratory parameters","volume":"14","author":"Spadaro","year":"1996","journal-title":"Clin Exp Rheumatol"},{"key":"2025092322201201000_11.3.e006019.3","doi-asserted-by":"publisher","DOI":"10.1136\/ard.50.6.362"},{"key":"2025092322201201000_11.3.e006019.4","doi-asserted-by":"crossref","first-page":"2951","DOI":"10.1007\/s10067-020-05065-9","article-title":"Elevated CRP even at the first visit to a rheumatologist is associated with long-term poor outcomes in patients with psoriatic arthritis","volume":"39","author":"Haroon","year":"2020","journal-title":"Clin Rheumatol"},{"key":"2025092322201201000_11.3.e006019.5","doi-asserted-by":"crossref","DOI":"10.1177\/1759720X221122417","article-title":"Normal C-reactive protein in active psoriatic arthritis: results from real-world clinical practice","volume":"14","author":"Gialouri","year":"2022","journal-title":"Ther Adv Musculoskelet Dis"},{"key":"2025092322201201000_11.3.e006019.6","doi-asserted-by":"publisher","DOI":"10.3899\/jrheum.141359"},{"key":"2025092322201201000_11.3.e006019.7","doi-asserted-by":"crossref","first-page":"368","DOI":"10.1038\/nrneph.2017.51","article-title":"The immunology of atherosclerosis","volume":"13","author":"Gister\u00e5","year":"2017","journal-title":"Nat Rev Nephrol"},{"key":"2025092322201201000_11.3.e006019.8","doi-asserted-by":"publisher","DOI":"10.1016\/j.neuron.2020.06.002"},{"key":"2025092322201201000_11.3.e006019.9","doi-asserted-by":"publisher","DOI":"10.1038\/nri1937"},{"key":"2025092322201201000_11.3.e006019.10","doi-asserted-by":"crossref","first-page":"15725","DOI":"10.1038\/ncomms15725","article-title":"Adipocyte adaptive immunity mediates diet-induced adipose inflammation and insulin resistance by decreasing adipose Treg cells","volume":"8","author":"Deng","year":"2017","journal-title":"Nat Commun"},{"key":"2025092322201201000_11.3.e006019.11","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1080\/03009742.2020.1803398","article-title":"Lessons learned from clinical phenotypes in early psoriatic arthritis: the real-world Dutch south west Early Psoriatic ARthritis study","volume":"50","author":"Kasiem","year":"2021","journal-title":"Scand J Rheumatol"},{"key":"2025092322201201000_11.3.e006019.12","doi-asserted-by":"crossref","DOI":"10.3390\/jcm10132834","article-title":"In Patients with Early Peripheral Psoriatic Arthritis Baseline C-Reactive Protein, Pain and Ultrasound-Detected Synovitis Predict Subsequent Treatment with ts\/bDMARDs. 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