Equating and linking Patient-Reported Outcomes Measurement Information System 29-item questionnaire and 36-item...

Area of Science:

• Health Outcomes Research
• Psychometrics
• Health Services Research

Background:

• The 36-item Short-Form Health Survey (SF-36) and the Patient-Reported Outcomes Measurement Information System 29-item questionnaire (PROMIS-29) are widely used patient-reported outcome measures.
• Comparing results across studies using different instruments can be challenging due to differing scoring metrics.

Purpose of the Study:

• To develop a practical methodology for equating or linking equivalent domains of the SF-36 and PROMIS-29.
• To utilize the Rasch framework for accurate score comparison between the two health surveys.
• To enable seamless data integration and analysis across studies employing either the SF-36 or PROMIS-29.

Main Methods:

• A Partial Credit Model was applied to common items from the SF-36 and PROMIS-29 within each domain.
• Data from 1501 French individuals representative of the general population were used for calibration.
• Items from both questionnaires were calibrated onto a common metric using Rasch modeling.

Main Results:

• Successful equating or linking was achieved for six of seven PROMIS-29 scales and five of six SF-36 subscales.
• Correspondence tables with 95% confidence intervals were generated for each equated domain.
• A user-friendly Stata macro was created to automate the equating process.

Conclusions:

• The developed methodology simplifies score comparison between SF-36 and PROMIS-29 in France.
• The Rasch-based equating process is practical, easily implementable, and applicable to other instruments and populations.
• This facilitates more robust meta-analyses and comparative effectiveness research.