Validation of the Restless Legs Syndrome Quality of Life Instrument q (RLS-QLI): Findings of a Consortium of National Experts and the RLS Foundation 1 M.J. Atkinson, R.P. Allen, J. DuChane, C. Murray, C. Kushida, T. Roth & the RLS Quality of Life Consortium 1 Global Outcomes Research, Pharmacia Corporation, Kalamazoo, MI, USA (E-mail: mark.j.atkinson@phar- macia.com) Accepted in revised form 22 april 2003 Abstract 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 a‘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 ¼ 0.47–0.60) and criterion-related validity was shown using the clinical IRLS Scale of Symptom Severity (r ¼ )0.45 to )0.77). Conclusion: The RLS-QLI is a valid disease-specific HRQL in- strument that will contribute to our understanding of how RLS impacts the lives of those affected with this CNS disorder. Key words: CNS disorder, Patient-reported outcome (PRO) measurement, Quality of life, Restless Legs Syndrome (RLS), Sleep disorder q The RLS-QLI is owned and maintained by the RLS Foundation. Permission to use the instrument, free of charge, must be sought from the RLS Foundation (http://www.rls.org/research). Independent reproduction of the RLS-QLI is not permitted. 1 Quality of Life Consortium: Clinical Members: Richard P. Allen, Neurology and Sleep Medicine, Johns Hopkins University, Baltimore, MD, USA. William Dement, Stanford Sleep Research Center, Stanford, CA, USA. Patrick Hogan, Puget Sound Regional Movement Disorders Clinic, Tacoma, WA, USA. Clete Kushida, Stanford Sleep Disorders Clinic and Research Center, Stanford, CA, USA. Tom Roth, Sleep Center, Henry Ford Hospital, Detroit, MI, USA. RLS Foundation Members: Georgiana Bell, Executive Director, RLS Foundation, Rochester, MN, USA. Cate Murray, Director of Research, RLS Foundation, Rochester, MN, USA. Pharmacia Members: Mark J. Atkinson, Research Scientist, Pharmacia Corporation, Kalamazoo, MI, USA. Janeen DuChane, Research Scientist, Pharmacia Corporation, Kalamazoo, MI, USA. Quality of Life Research 13: 679–693, 2004. Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands. 679