Assessing domain match and feasibility of candidate instruments matching with OMERACT endorsed domains to measure flare in knee and hip osteoarthritis.

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.

Development and validation of the Flare-OA questionnaire for measuring flare in knee and hip osteoarthritis.

OBJECTIVE: Ability to assess flares in osteoarthritis (OA) of the knee and hip (KHOA) is important in clinical care and research. Using mixed methods, we developed a self-reported instrument measuring flare and assessed its psychometric properties. METHODS: We constructed questionnaire items from semi-structured interviews and a focus group (patients, clinicians) by using a dual-language (English-French) approach. A Delphi consensus method was used to select the most relevant items. Patients with OA from Australia, France and the United States completed the preliminary Flare-OA, HOOS, KOOS and Mini-OAKHQOL questionnaires online. We used a factor analysis and content approach to reduce items and determine structural validity. We tested the resulting questionnaire (score 0-100) for internal consistency, convergent and known-groups validity. RESULTS: Initially, 180 statements were generated and reduced to 33 items in five domains (response 0 = not at all, to 10 = absolutely) by Delphi consensus (50 patients, 116 professionals) and an expert meeting. After 398 patients (mean [SD] age 64 [8.5] years, 70.4% female, 86.7% knee OA) completed the questionnaire, it was reduced to 19 items by factor analysis and a content approach (RMSEA = 0.06; CFI = 0.96; TLI = 0.94). The Cronbach's alpha was >0.9 for the five domains and the whole questionnaire. Correlation coefficients between Flare-OA and other instrument scores were as predicted, supporting construct validity. The difference in Flare-OA score between patients with and without flare (31.8) largely exceeded 2 SEM (10.2). CONCLUSION: Flare-OA is a valid and reliable patient-reported instrument for assessing the occurrence and severity of flare in patients with KHOA in clinical research.