Developing a common metric using current scales for assessing functioning in patients with knee osteoarthritis

Area of Science:

• Orthopedics
• Rheumatology
• Health Outcomes Research

Background:

• Multiple scales assess knee osteoarthritis (OA) functioning, leading to data heterogeneity.
• A unified approach is needed to standardize functional assessments in knee OA research and clinical practice.

Purpose of the Study:

• To develop a common metric (CM) for assessing functioning in knee OA patients.
• To enable interchangeable use and direct comparison of scores from various commonly used knee OA assessment scales.

Main Methods:

• A methodological study involving 411 knee OA patients.
• Data from six established scales were analyzed using concurrent calibration and the Rasch measurement model.
• Items focused on self-care, mobility, and domestic activities aligned with the ICF framework.

Main Results:

• The developed CM demonstrated good reliability (person separation index of 0.827).
• The CM met Rasch model assumptions, including unidimensionality and local independence.
• Item functions were not significantly affected by age, sex, or disease duration.

Conclusions:

• A reliable common metric (CM) was successfully created for knee OA functioning assessment.
• The CM facilitates score comparison and interchangeable use across different scales.
• This standardized approach aids clinicians and researchers in evaluating knee OA patient function.