The Preference-Based Multiple Sclerosis Index: an assessment of its psychometric properties and translation into Turkish

Abstract

Purpose

To translate Preference-Based Multiple Sclerosis Index (PBMSI) into Turkish, investigate its psychometric properties and differences between its two scoring algorithms: PBMSI-Rating Scale (PBMSI-RS) and PBMSI-Standard Gamble (PBMSI-SG).

Methods

An expert committee supervised the translation process. Psychometric properties were evaluated in 104 people with multiple sclerosis. Exploratory common factor analysis was used to investigate structural validity. Convergent validity was assessed by formulating hypotheses about correlations between PBMSI and other HRQL measures, disability level, walking-related measures, and MS symptoms. Known-groups validity was assessed against different measures of disability and walking capacity. Test-retest reliability was assessed by calculating the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable change (MDC95%).

Results

Factor analysis revealed one factor (Eigenvalue = 2.46). PBMSI-RS and PBMSI-SG correlated significantly with other measures (p < .001). Both could differentiate between individuals with different levels of disability and walking capacity (p < .05, d  ≥  0.50). Relative test-retest reliability was moderate for PBMSI-RS (ICC = 0.75) and good for PBMSI-SG (ICC = 0.83). SEM and MDC95% values were 0.16 and 0.44 for PBMSI-RS and 0.10 and 0.28 for PBMSI-SG, respectively.

Conclusion

Turkish version of PBMSI has good psychometric properties to assess health-related quality of life in people with multiple sclerosis. PBMSI-SG should be preferred over PBMSI-RS.

IMPLICATIONS FOR REHABILITATION

• Health-related quality of life is often used as a primary or secondary endpoint in multiple sclerosis research.

• The Preference-Based Multiple Sclerosis Index is the first preference-based health-related quality of life measure developed in multiple sclerosis using patient preferences.

• Preference-Based Multiple Sclerosis Index was translated to Turkish and demonstrated good psychometric properties, including structural, convergent, known-groups validity, internal consistency, and test-retest reliability.

• Professionals working in the field of multiple sclerosis research and rehabilitation may benefit from using the Preference-Based Multiple Sclerosis Index as it is a short and psychometrically robust instrument.

Keywords:

• Multiple sclerosis
• health-related quality of life
• patient outcome assessments
• Turkish
• Turkey

Acknowledgments

The authors thank the Multiple Sclerosis Research Association staff for their help during the recruitment of the participants, expert committee members for their valuable contributions, and all participants for their willingness to participate. We sincerely thank Dr. Ayse Kuspinar for granting permission to conduct the Turkish validation study, her contribution throughout the translation and validation process, and her comments on the draft manuscript. This study was not registered in a public repository.

Disclosure statement

No potential conflict of interest was reported by the author(s).