Relation of the International Restless Legs Syndrome Study Group Rating Scale with the Clinical Global Impression Severity Scale, the Restless Legs Syndrome 6-item Questionnaire, and the Restless Legs Syndrome-quality of Life Questionnaire

Background: The SP790 study (ClinicalTrials.gov, NCT00136045) showed benefits of rotigotine over placebo in improving symptom severity of restless legs syndrome (RLS), also known as Willis-Ekbom disease, on the International Restless Legs Syndrome Study Group rating scale (IRLS), Clinical Global Impression item 1 (CGI-1), RLS 6-item questionnaire (RLS-6), and the RLS-quality of life questionnaire (RLS-QoL) in patients with moderate to severe idiopathic RLS. To provide clinical context for the IRLS and to guide the choice of assessment scales for RLS studies, our post hoc analysis of SP790 data evaluated associations between the IRLS and the CGI-1, IRLS and RLS-6, and the IRLS and RLS-QoL.

Methods: Scale associations were analyzed at baseline and at the end of maintenance (EoM) using data from the safety set (rotigotine and placebo groups combined [n=458]). Changes from baseline to EoM in IRLS score vs comparator scale scores also were analyzed.

Results: There was a trend towards increasing IRLS severity category with increasing CGI-1, RLS-6, and RLS-QoL score. Pearson product moment correlation coefficients showed correlations between IRLS and comparator scale scores at baseline and EoM as well as correlations for change from baseline to EoM.

Conclusion: Correlations between the IRLS and comparator scales were substantial. These data indicate that the IRLS is clinically meaningful. The IRLS and CGI-1 are generally sufficient to evaluate the overall severity and impact of RLS symptoms in clinical trials.