How Much Improvement in Functional Status Is Considered Important by Patients With Active Psoriatic Arthritis: Applying the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) Group Guidelines Philip Mease 1 Rita Ganguly 2, L. Wanke 3, Amitabh Singh 2 1 Seattle Rheumatology Associates, Seattle, WA; 2 Wyeth Research, Collegeville, PA; 3 Amgen, Thousand Oaks, CA

Objectives To estimate MCID based on OMERACT Group recommendation, for characterizing between- treatment group, within-group, and within-subject improvements in functional status of patients with Psoriatic Arthritis (PsA)

Methods Data from a double blind, randomized, placebo controlled 24 weeks study was used to assess patients with active Psoriatic Arthritis treated with etanercept 25 mg twice weekly compared to placebo Alternative measures of MCID for improvement in patients’ functional status as measured by Health Assessment Questionnaire (HAQ) were: –Data-driven MCID: –Patient Rating-Based MCID: –Patient Rating-Based Important MCID: 2.1.5

Methods Data-Driven Approach MCID Upper bound of 95% confidence interval of standard error of measurement (SEM) for HAQ SEM = σ baseline HAQ 1- r baseline HAQ where σ=standard deviation r = Cronbach’s alpha coefficient

Methods Patient Rating-Based MCID How important to you is the amount of change in your physical limitations (such as limitations in walking, standing, gripping reaching, etc.) Not AtExtremely All Important Important Mean change from baseline in HAQ Disability Score for those who improved Minimally Important Very Important

GroupsAgeHAQDuration Etanercept years Placebo years Results Baseline Characteristics

Results

Mean Change of HAQ Scores from Baseline were Clinically Meaningful for Patients Treated with Etanercept 25 mg twice weekly

Results Weeks Percent Percent Achieving SEM Based MCID in HAQ Threshold

Conclusions Improvements of 0.30 in HAQ score are considered “minimally important” by patients with active PsA. A threshold of 0.30 may be used to characterize within- treatment group changes in the HAQ Disability Index. A higher threshold of 0.40 should be used to characterize within-subjects improvements in the HAQ Disability Index.

Valued Life Activities (VLA) Broader array of activities than measured by HAQ, e.g. ability to take part in social activities, taking care of family members, participating in religious activities, etc. Element of motivation Importance of meaningfulness

VLA Katz P Arth Care & Research 1995 RA patients with decline in basic function and/or loss of valued activities Deline in basic function (HAQ), no loss of valued activities (30%) Loss of valued activities, no decline in basic function (57%) Both (13%)