Application of the OMERACT filter to measures of core outcome domains in recent clinical studies of acute gout.

Objective: To determine the extent to which instruments that measure core outcome domains in acute gout fulfill the Outcome Measures in Rheumatology (OMERACT) filter requirements of truth, discrimination, and feasibility.

Methods: Patient-level data from 4 randomized controlled trials of agents designed to treat acute gout and 1 observational study of acute gout were analyzed. For each available measure, construct validity, test-retest reliability, within-group change using effect size, between-group change using the Kruskall-Wallis statistic, and repeated measures generalized estimating equations were assessed. Floor and ceiling effects were also assessed and minimal clinically important difference was estimated. These analyses were presented to participants at OMERACT 11 to help inform voting for possible endorsement.

Results: There was evidence for construct validity and discriminative ability for 3 measures of pain [0 to 4 Likert, 0 to 10 numeric rating scale (NRS), 0 to 100 mm visual analog scale (VAS)]. Likewise, there appears to be sufficient evidence for a 4-point Likert scale to possess construct validity and discriminative ability for physician assessment of joint swelling and joint tenderness. There was some evidence for construct validity and within-group discriminative ability for the Health Assessment Questionnaire as a measure of activity limitations, but not for discrimination between groups allocated to different treatment.

Conclusion: There is sufficient evidence to support measures of pain (using Likert, NRS, or VAS), joint tenderness, and swelling (using Likert scale) as fulfilling the requirements of the OMERACT filter. Further research on a measure of activity limitations in acute gout clinical trials is required.