Linking the KOOS-PS to PROMIS Physical Function in Knee Patients Evaluated for Surgery

Area of Science:

• Orthopaedic research
• Biostatistics
• Patient-reported outcome measures

Background:

• The Knee Injury and Osteoarthritis Outcome Score-Physical Function Short-form (KOOS-PS) and Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function are vital patient-reported outcome measures (PROMs) in orthopaedics.
• Comparing data across different PROMs is challenging but essential for clinical practice and research.

Purpose of the Study:

• To develop a crosswalk table linking KOOS-PS and PROMIS Physical Function scores.
• To enable direct comparison of physical function data collected using these two widely adopted instruments.

Main Methods:

• Employed five linking methods, including item response theory (IRT)-based and equipercentile methods.
• Validated linking assumptions such as content similarity, unidimensionality, and population invariance.
• Evaluated method performance using statistical metrics like mean difference, standard deviation, and root-mean-squared deviation.

Main Results:

• Linking assumptions were met, supporting the validity of the crosswalk.
• The Stocking-Lord method yielded the most favorable results, with minimal mean difference, standard deviation, and root-mean-squared deviation.
• The derived crosswalk was successfully validated in independent patient samples.

Conclusions:

• A practical crosswalk table was created to facilitate score conversion between KOOS-PS and PROMIS Physical Function.
• This tool will enhance the interpretation and aggregation of physical function outcomes in knee condition research and clinical evaluation.
• Standardizing outcome measure comparisons aids in understanding patient functional status more effectively.