The Preference-Based Multiple Sclerosis Index (PBMSI)

Health-related quality of life (HRQL) in multiple sclerosis (MS) is multidimensional, and represented by the domains of physical, mental, and social well-being. One method of measuring HRQL is through the use of health profiles. Existing MS-specific health profiles are scored by subscale or domain, and fail to provide a single summary score of HRQL. For example, if a treatment has a positive effect on physical health but a negative one on mental health, it is impossible to determine whether the intervention resulted in a net improvement or decline in HRQL, unless one knows the relative importance attached to each domain.

Another approach to measuring HRQL is through the use of preference-based measures. Preference-based measures attach a value to each domain of health, and provide a single summary index from 0 (dead) to 1 (perfect health). Existing preference-based measures that have been used in MS are generic in nature. Semi-structured interviews with MS patients [1] revealed that many domains of health that were important to people with MS were missing from generic preference based measures. Furthermore, preferences for these measures were based on the perspective of the general public, who had either none or little experience of the health states that they were asked to value. Although general population weights are important for economic evaluation and quality-adjusted life years (QALYs), they have little relevance in clinical research and decision-making.

To address this knowledge gap, we interviewed 185 people with MS, diagnosed in the era of disease modifying therapies and MRI, to identify the domains that were most important to the HRQL of people with MS. Optimally performing items targeting the important MS domains were identified using Rasch Analysis, and were tested for their discriminatory capacity with respect to known groups with differing disability. [2] A set of 5 bilingual items (English and French) were identified, and tested for comprehension and wording using cognitive interviewing with people with MS.[3] The final product was a health classification system specific for people with MS: the Preference-Based Multiple Sclerosis Index (PBMSI).
The PBMSI consists of five items: walking, fatigue, mood, concentration, and roles and responsibilities. Each item has three response options, and the recall time frame is ‘over the past week’. The classification system can produce 243 (35) possible health states.
Patient preferences for the PBMSI health states have been elicited using two different methods of preference elicitation: the Standard Gamble and the Rating Scale. The Standard Gamble was not practical in this patient population, as patients had difficulty understanding the task and were not willing to risk death for an improvement in health. On the other hand, the Rating Scale was found to be more suitable for people with MS. A preliminary scoring algorithm based on a sample of 61 patients is available for the PBMSI. The scoring algorithm demonstrated evidence of construct validity in a sample of MS patients participating in a clinical trial (n=64).
Preference weights are currently being elicited on a sample of 200 patients with MS, and will be used to finalize the scoring algorithm for the PBMSI. Validation of the algorithm, both cross-sectionally and longitudinally will be performed. The PBMSI will provide a single value of HRQL from 0 (dead) to 1 (perfect health). This value can be used to describe HRQL across persons, place and time, as well as evaluate the clinical and cost-effectiveness of different interventions (pharmaceutical, rehabilitative, or psychosocial) for people with MS.
For further information on the PBMSI please contact:
ayse.kuspinar@mail.mcgill.ca or nancy.mayo@mcgill.ca
 
References
1. Kuspinar, A., & Mayo, N. E. (2013). Do generic utility measures capture what is important to the quality of life of people with multiple sclerosis. Health Qual Life Outcomes, 11(1), 71.
2. Kuspinar, A., Finch, L., Pickard, S., & Mayo, N. E. (2014). Using existing data to identify candidate items for a health state classification system in multiple sclerosis. Quality of Life Research, 23(5), 1445-1457.
3. Kuspinar, A., Bouchard, V., Moriello, C., & Mayo, N. E. (2015). The Development of a Bilingual MS-Specific Health Classification System: The Preference-Based Multiple Sclerosis Index (PBMSI). International Journal of MS Care (Online First).
 
PREFERENCE-BASED MULTIPLE SCLEROSIS INDEX
For each of the items listed below, choose the option you were most often in, over the past week.
1) Walking
Describe your ability to walk in the past week.
Most often:
☐ I could walk briskly for recreation or sports
☐ I could walk to accomplish the tasks I needed to do during the day (to and from transportation, public building or within work environment)
☐ I could walk only a few steps or I always used a wheelchair
2) Fatigue
Describe your fatigue in the past week.
Most often:
☐ I never felt so tired that I had to rest
☐ I felt so tired that I had to rest one or more times throughout the day
☐ I felt so tired that I had to rest most of the day
3) Mood
Describe your mood in the past week.
Most often:
☐ I did not feel sad or depressed
☐ I felt somewhat sad or depressed
☐ I felt very sad or depressed
4) Concentration
Did you have trouble concentrating in the past week (on things like conversations, books, movies or daily routines)?
Most often:
☐ I never or rarely had trouble
☐ I had trouble some of the time
☐ I had trouble most of the time
5) Roles & responsibilities
Describe your ability to do the things you needed to do at work, at home, and to take care of yourself and your family in the past week.
Most often:
☐ I could do all or most of the things I needed to do
☐ I could do some of the things I needed to do
☐ I could not do the things I needed to do