Quality of life in multiple sclerosis: development and validation of the 'RAYS' scale and comparison with the SF-36

To develop a self-administered rating scale for quantifying quality of life (QoL) in multiple sclerosis (MS) patients.

The RAYS scale items were derived from a source of 600 questions composed by our Centre's experts from commonly used instruments that assess physical, psychological, and social-familial dimensions. Prior to finalization of the RAYS QoL, candidate items were administered to 15 health rehabilitation professionals. Clarity, importance, relevance and specificity were graded for each item by every professional independently. Items chosen for the final version were graded as good or excellent on all these aspects. The Medical Outcome Study Short Form-36 (SF-36) was used to compare health appraisal with the RAYS scale.

Each of the three subscales of the RAYS covers a different dimension (physical, psychological, and social-familial) and each includes 15 self-report items scored from 1 (best) to 4 (worse), focusing on the preceding week. Validation was achieved through administration of the scale to 50 randomly selected MS patients and to 50 age, sex-, education- and family status-matched healthy controls. All RAYS dimensions among MS patients reached a Cronbach's coefficient alpha > 0.8. Mean values for all dimensions were greater in patients than in controls (P < 0.002). Patients scored below norms for the general population in the majority of the SF-36 subscales (on average 32% lower). Significant correlation was found between the two scales especially in the physical and social functioning subscales.

The RAYS scale demonstrated high internal consistency and significant discriminative value, and is thus a suitable disease-specific tool for measuring QoL in MS.