Objectives: The Outcome Measures in Rheumatology Initiative established the Contextual Factors Working Group to guide the understanding, identification and handling of contextual factors for clinical trials. In clinical research, different uses of the term 'contextual factors' exist. This study explores the perspectives of researchers (including clinicians) and patients in defining 'contextual factor' and its related terminology, identifying such factors and accounting for them in trials across rheumatology., Methods: We conducted individual semistructured interviews with researchers (including clinicians) who have experience within the field of contextual factors in clinical trials or other potentially relevant areas, and small focus group interviews with patients with rheumatic conditions. We transcribed the interviews and applied qualitative content analysis., Results: We interviewed 12 researchers and 7 patients. Researcher's and patient's descriptions of contextual factors were categorised into two broad themes, each comprising two contextual factors types. The 'treatment effect' theme focused on factors explaining variations in treatment effects (A) among patients and (B) among studies. The 'outcome measurement' theme focused on factors that explain (C) variations in the measurement result itself (apart from actual changes/differences in the outcome) and (D) variations in the outcome itself (beside treatment of interest). Methods for identifying and handling contextual factors differed among these themes and types., Conclusions: Two main themes for contextual factors with four types of contextual factors were identified based on input from researchers and patients. This will guide operationalisation of contextual factors. Further research should refine our findings and establish consensus among relevant stakeholders., Competing Interests: Competing interests: AB received a research grant from Abbvie, and an honorarium for lecture or advisory boards from UCB, Galapagos and Lilly; all financial support was paid to her department. DB reports that she is on the executive of OMERACT (Outcome Measurement in Rheumatological Research) and chair its methodology group; this did not influence this current written work. DEF reports grant/research support from Corbus, Galapagos Golead, GSK, NIH, Pfizer, Talaris, CSL Behring, as well as consultant for Abbvie, Amgen, Corbus, Galapagos, Gilead, Novartis, Pfizer, Roche/Genentech, Talaris, CSL Behring, Boehringer Ingelheim. JSS reports grants from Abbvie, AstraZeneca, Janssen, Lilly, Merck Sharpe and Dohme, Pfizer, and Roche, from AbbVie, Amgen, AstraZeneca, Astro, Bristol-Myers Squibb, Celgene, Celltrion, Chugai, Gilead, ILTOO Pharma, Janssen, Lilly, Merck Sharp and Dohme, Novartis-Sandoz, Pfizer, Roche, Samsung, Sanofi, and UCB., outside the submitted work. RC reports non-financial support from Board membership, grants from Consultancy (AbbVie, Amgen, Axellus A/S, Biogen, Bristol-Myers Squibb, Cambridge Weight Plan, Celgene, Eli Lilly, Hospira, MSD, Norpharma, Novartis, Orkla Health, Pfizer, Roche, Sobi, Takeda), personal fees from Employment (Research Unit for Musculoskeletal Function and Physiotherapy, Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark), non-financial support from Expert testimony, grants from Grants/grants pending (Axellus A/S, AbbVie, Cambridge Weight Plan, Janssen, MSD, Mundipharma, Novartis, and Roche), grants from Payment for lectures including service on speakers bureaus (Abbott, Amgen, Axellus, Bayer HealthCare Pharmaceuticals, Biogen Idec, Bristol-Myers Squibb, Cambridge Weight Plan, Ipsen, Janssen, Laboratoires Expanscience, MSD, Mundipharma, Norpharma, Novartis, Pfizer, Roche, Rottapharm-Madaus, Sobi, and Wyeth), grants from Payment for manuscript preparation (Axellus, Bristol-Myers Squibb, and Cambridge Weight Plan, Aleris-Hamlet (via Norpharma)), non-financial support from Patents (planned, pending or issued), non-financial support from Royalties, grants from Payment for development of educational presentations (Bristol-Myers Squibb, MSD, Pfizer), non-financial support from Stock/stock options, grants from Travel/accommodations/meeting expenses unrelated to activities listed (Abbott, AbbVie, Axellus, Biogen, Bristol-Myers Squibb, Cambridge Weight Plan, Celgene, Laboratoires Expanscience, Norpharma, Novartis, Pfizer, Roche, Rottapharm-Madaus, and Wyeth), non-financial support from Other (err on the side of full disclosure), outside the submitted work; and he is involved in many health-care initiatives and research that could benefit from wide uptake of this publication (including Cochrane, OMERACT, IDEOM, RADS, and the GRADE Working Group); Musculoskeletal Statistics Unit, The Parker Institute is grateful for the financial support received from public and private foundations, companies and private individuals over the years. PT reports other from Amgen, Astra Zeneca, Bristol Myers Squibb, Celgene, Eli Lilly, Genentech/ Roche, Genzyme / Sanofi, Horizon Pharma Inc., Merck, Novartis, Pfizer, PPD, Quintiles, Regeneron, Savient, Takeda Pharmaceutical, UCB Group, Vertex, Forest, Bioiberica, personal fees from UCB Biopharma and SPRL, Parexel International, Prahealth Sciences, personal fees from CHEOR Solutions (Canada), Innovative Science Solutions, Reformulary Group, other from Elsevier, Little Brown, Wolters Kluwer and John Wiley & Sons, other from Abbott, Roche, Schering Plough/Merck, UCB, BMS, outside the submitted work; and Peter Tugwell is the recipient of Canada Research Chair in Health Equity (Tier 1-2016–2024) from the Canadian Institutes of Health Research., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.) more...