Measuring Inflammatory Foot Disease in Rheumatoid Arthritis: Development and Validation of the Rheumatoid Arthritis...

Area of Science:

• Rheumatology
• Clinical Measurement
• Patient-Reported Outcomes

Background:

• Rheumatoid arthritis (RA) disease activity indices may underestimate foot involvement.
• Accurate assessment of foot disease activity is crucial for effective RA management and treatment.

Purpose of the Study:

• To evaluate the measurement properties of the Rheumatoid Arthritis Foot Disease Activity Index-5 (RADAI-F5).
• To establish RADAI-F5 as a valid, reliable, and responsive patient-reported outcome measure for foot disease in RA.

Main Methods:

• Participants with RA completed RADAI-F5, mRADAI-5, FFI, FIS, and DAS28-ESR.
• Psychometric properties including validity, internal consistency, reproducibility, and responsiveness were assessed.
• Subgroups completed RADAI-F5 at baseline, 1 week, and 6 months for longitudinal evaluation.

Main Results:

• RADAI-F5 showed theoretically consistent associations with other RA measures, confirming construct validity.
• High internal consistency (Cronbach's α = 0.90) and good reproducibility (ICC = 0.868) were demonstrated.
• Content validity was confirmed, with 82% finding the instrument relevant and easy to understand.

Conclusions:

• The RADAI-F5 is a valid, reliable, and responsive patient-reported outcome measure.
• It is clinically feasible for assessing foot disease activity in individuals with RA.
• This index can help prevent underestimation of foot and overall disease activity in RA.