Validation of the Restless Legs Syndrome quality of life instrument (RLS-QLI): Findings of a consortium of national experts and the RLS Foundation

This study was designed to assess the initial psychometric properties of a new disease-specific health-related quality of life (HRQL) measure, the Restless Legs Syndrome (RLS) Quality of Life Instrument (RLS-QLI). Methods: Draft items were generated from a literature review, consultation with MD and PhD specialists in the fields of neurology and sleep medicine, and input from two patient focus groups. The initial item reduction was accomplished using a survey of 392 persons with self-reported RLS symptoms from the membership of the RLS Foundation. The final ( independent) validation sample consisted of 574 of persons on the RLS Foundation's Interest Group List Serve who also reported having RLS. The mean age of participants was 54.5 (SD 12.3), with a sex ratio of 1M: 2F, and the majority was on some form of medication for RLS (66%). Results: Four factors were identified ( Daily Function, Social Function, Sleep Quality, and Emotional Well-Being) consisting of 17 items that explained 73.3% of the total variance. Each scale had good internal consistency (Cronbach's alpha' s between 0.85 and 0.91) and 2-week test - retest stability (Pearson Correlations between 0.81 and 0.93). Convergent validity was demonstrated using related scales on the SF-36 (r = 0.47 - 0.60) and criterion-related validity was shown using the clinical IRLS Scale of Symptom Severity (r = -0.45 to -0.77). Conclusion: The RLS-QLI is a valid disease-specific HRQL instrument that will contribute to our understanding of how RLS impacts the lives of those affected with this CNS disorder.