OBJECTIVE: To assess the role of the anti-TIF1γ auto-antibody (aAb) IgG2 isotype as a biomarker of cancer in anti-TIF1γ aAb-positive adult DM. METHODS: International multicentre retrospective study with the following inclusion criteria: (i) diagnosis of DM according to ENMC criteria; (ii) presence of anti-TIF1γ IgG aAb determined using an in-house addressable laser bead immunoassay (ALBIA) from cryopreserved serums sampled at time of DM diagnosis and (iii) available baseline characteristics and follow-up data until the occurrence of cancer and/or a minimum follow-up of 1 year for patients without known cancer at diagnosis. Detection and quantification of anti-TIF1γ IgG2 aAb was done using the in-house ALBIA. In addition, a recent ELISA commercial kit was used for anti-TIF1γ IgG aAb quantification. RESULTS: A total of 132 patients (mean age 55±15 years) of whom 72 (54.5%) had an associated cancer were analysed. The association between the presence of cancer and the presence of anti-TIF1γ IgG2 aAb was statistically significant (P = 0.026), with an OR of 2.26 (95% CI: 1.10, 4.76). Patients with cancer displayed significantly higher anti-TIF1γ IgG2 aAb ALBIA values with a median value of 1.15 AU/ml (IQR: 0.14-9.76) compared with 0.50 AU/ml (IQR: 0.14-1.46) for patients without cancer (P = 0.042). In addition, patients with cancer displayed significantly higher anti-TIF1γ IgG aAb ELISA values with a median value of 127.5 AU/ml (IQR: 81.5-139.6) compared with 93.0 AU/ml (IQR: 54.0-132.9) for patients without cancer (P = 0.004). CONCLUSION: These results suggest considering anti-TIF1γ IgG2 ALBIA and IgG ELISA values as biomarkers of cancer in anti-TIF1 γ aAb-positive adult DM.

Centre d'Investigation Clinique Antilles Guyane INSERM CIC 1424 Pointe à Pitre Guadeloupe

Department of Dermatology and Clinical Immunology Guadeloupe University Hospital Pointe à Pitre Guadeloupe

Department of Dermatology University of Pennsylvania and Corporal Michael L Creszenc VAMC Philadelphia PA USA

Department of Immunology and Biotherapy Rouen University Hospital Rouen France

Department of Internal Medicine Vall d'Hebron Hospital Universitat Autònoma Barcelona Spain

Department of Medicine University of Montreal Montreal Quebec Canada

Department of Rheumatology 1st Medical Faculty Charles University Praha Czech Republic

Department of Rheumatology Salford Royal Hospital Northern Care Alliance NHS Foundation Trust Manchester Academic Health Science Centre Salford UK

Division of Musculoskeletal and Dermatological Sciences School of Biological Sciences University of Manchester Manchester UK

Division of Rheumatology and Research Center Centre Hospitalier de l'Université de Montréal Montreal Quebec Canada

Division of Rheumatology Department of Medicine Karolinska Institute Stockholm Solna Sweden

Epidemiology and Public Health Group School of Health Sciences University of Manchester Manchester UK

Institute of Rheumatology Na Slupi 4 Praha 2 Czech Republic

ME Gastro Derm Rheuma Karolinska University Hospital Stockholm Sweden

National Institute for Health Research Manchester Biomedical Research Centre Manchester University NHS Foundation Trust The University of Manchester Manchester UK

Univ Rouen Normandie FOCIS Center of Excellence PAn'THER Inserm U1234 Rouen France

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