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.