RESUMEN
PURPOSE: To evaluate the domain match (truth) and feasibility of candidate instruments assessing flare in knee and hip osteoarthritis (OA) according to the identified domains. MATERIAL AND METHODS: From a literature review (575 papers), instruments were selected and evaluated using the truth and feasibility elements of the OMERACT Filter 2.2. These were evaluated by 26 experts, including patients, in two Delphi survey rounds. The final selection was obtained by a vote. RESULTS: 44 instruments were identified. In Delphi Round 1, five instruments were selected. In Round 2, all instruments obtained at least 75 % in terms of content match with the endorsed domains and feasibility. In the final selection, the Flare-OA questionnaire obtained 100 % favorable votes. CONCLUSION: Through consensus of the working group, the Flare-OA questionnaire was selected as the best candidate instrument to move into a full assessment of its measurement properties using the OMERACT Filter 2.2.