{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T17:37:10Z","timestamp":1772645830198,"version":"3.50.1"},"reference-count":28,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T00:00:00Z","timestamp":1772582400000},"content-version":"unspecified","delay-in-days":62,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["82071965"],"award-info":[{"award-number":["82071965"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["82472013"],"award-info":[{"award-number":["82472013"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2023YFF0716000"],"award-info":[{"award-number":["2023YFF0716000"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2024YFC2419800"],"award-info":[{"award-number":["2024YFC2419800"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["RMD Open"],"accepted":{"date-parts":[[2026,2,3]]},"published-print":{"date-parts":[[2026,1]]},"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>\n                      <jats:sup>18<\/jats:sup>\n                      F-Fibroblast activation protein inhibitor ([\n                      <jats:sup>18<\/jats:sup>\n                      F]FAPI) positron emission tomography (PET)\/CT is an emerging tool for detecting IgG4-related disease (IgG4-RD). However, standardised quantitative analysis and image scoring present ongoing challenges in patients with IgG4-RD.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose<\/jats:title>\n                    <jats:p>\n                      To establish organ-specific reference thresholds for IgG4-RD involvement on [\n                      <jats:sup>18<\/jats:sup>\n                      F]FAPI PET\/CT images, and to develop a novel, clinically applicable scoring system to monitor disease activity in patients with IgG4-RD.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      This retrospective study recruited 85 patients with IgG4-RD and 10 healthy individuals, all of whom underwent [\n                      <jats:sup>18<\/jats:sup>\n                      F]FAPI PET\/CT. Organ-specific uptake thresholds were defined as [\n                      <jats:sup>18<\/jats:sup>\n                      F]FAPI uptake greater than the maximal standardised uptake value +3 SD in the corresponding anatomical regions of healthy individuals. Moreover, we developed a novel method, [\n                      <jats:sup>18<\/jats:sup>\n                      F]FAPI PET\/CT Activity Score of IgG4-RD (FPAS-IgG4), for scoring disease activity using a logistic regression model with receiver operating characteristics curve analysis.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Among 85 patients with IgG4-RD, 64 lesions suspected of IgG4-RD involvement were biopsied and 58 (90.6%) of these lesions were positive for IgG4. [\n                      <jats:sup>18<\/jats:sup>\n                      F]FAPI PET\/CT achieved a sensitivity, specificity and accuracy of 86.2%, 83.3% and 85.9%, respectively, for detecting IgG4-RD based on organ-specific uptake thresholds. The active disease group had a higher FPAS-IgG4 than the inactive disease group (5.2\u00b13.0 vs 1.7\u00b11.3, p&lt;0.0001). FPAS-IgG4 &gt;2 showed a sensitivity of 93.2% and a specificity of 73.1% in distinguishing between active and inactive disease. Multivariable logistic regression analysis demonstrated that FPAS-IgG4 was strongly associated with active IgG4-RD (p=0.001).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>\n                      [\n                      <jats:sup>18<\/jats:sup>\n                      F]FAPI PET\/CT could be a valuable tool for monitoring the activity of IgG4-RD, aiding in disease stratification.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/rmdopen-2025-006540","type":"journal-article","created":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T14:05:15Z","timestamp":1772633115000},"page":"e006540","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["[\n                    <sup>18<\/sup>\n                    F]FAPI PET\/CT-based scoring systems for patient assessment in IgG4-related disease"],"prefix":"10.1136","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3388-7907","authenticated-orcid":false,"given":"Donghe","family":"Chen","sequence":"first","affiliation":[{"name":"Department of Nuclear Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-9672-5521","authenticated-orcid":false,"given":"Danqing","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Rheumatology, Pujiang branch of the First Affiliated Hospital of Zhejiang University, Jinhua, Zhejiang, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1735-0966","authenticated-orcid":false,"given":"Chuanyin","family":"Sun","sequence":"additional","affiliation":[{"name":"Department of Rheumatology, The First Affiliated Hospital, Zhejiang University School 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