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).


CONCLUSIONS
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.
Atkinson
M J
MJ
Global Outcomes Research, Pharmacia Corporation, Kalamazoo, MI 49001, USA. mark.j.atkinson@pharmacia.com
Allen
R P
RP
DuChane
J
J
Murray
C
C
Kushida
C
C
Roth
T
T
D000328:Adult; D017668:Age of Onset; D000368:Aged; D003299:Cooperative Behavior; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011369:Professional-Patient Relations; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life; D012148:Restless Legs Syndrome / Q000503:physiopathology / Q000523:psychology*; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires / Q000592:standards*; D014481:United States