Validation of the Augmentation Severity Rating Scale (ASRS): A multicentric, prospective study with levodopa on restless legs syndrome

Abstract

Background: Augmentation is the main complication during long-term dopaminergic treatment of restless legs syndrome (RLS) and reflects an overall increase in RLS severity. Its severity varies considerably from a minor problem to a devastating exacerbation of disease. Despite its clinical relevance, systematic evaluations have rarely been undertaken and there has been no development of methods to assess the severity of augmentation. To fill this gap, the European RLS Study Group (EURLSSG) has developed the Augmentation Severity Rating Scale (ASRS), using three items that assess the degree of change in three specific dimensions of augmentation. The changes in each dimension are summed to give an ASRS total score. Methods: The ASRS was developed to cover the basic dimensions defining RLS augmentation. The items were developed by an interactive process involving professional and patient input. The ASRS that was evaluated included four major items and two alternative forms of one item. The validation was conducted using 63 (85%) mostly untreated RLS patients from six centers, who were treated for six months with levodopa (l-Dopa) (up to 500 mg/day, as clinically needed). Two consecutive assessments before and at baseline measured test-retest reliability. Consecutive ASRS ratings by two independent raters on a subsample of patients evaluated inter-rater reliability. Comparison with clinical severity ratings of two independent experts provided external validation of the ASRS. Comparison of patients with and without augmentation with regard to the items and the total score of the ASRS added discriminant validity. Results: Sixty patients (63% females, mean age: 53 years, baseline International RLS Severity Rating (IRLS) score 24.7 ± 5.2) were treated with a median daily dose of 300 mg l-Dopa (range: 50-500 mg). Thirty-six patients (60%) experienced augmentation. Item analyses indicated that one item could be removed as it did not contribute significantly to the test score and only one form of the duplicated item needed to be used. The final ASRS then included three items. Test-retest reliability for the total score was ρ = 0.72, and inter-rater reliability was rcc = 0.94. Cronbach's α was 0.62. Validity as assessed by the correlation between the worst ASRS total score during the trial and the expert rating was ρ = 0.72. ASRS total score differed between patients without versus with augmentation (mean: 7.4 (standard deviation (SD) = 4.0) vs. 2.0 (2.7) (P < 0.0001). Conclusions: The ASRS is a reliable and valid scale to measure the severity of augmentation. Due to the need to systematically quantify augmentation for both long-term efficacy and tolerability, the ASRS may become a useful tool to monitor augmentation in future clinical trials. © 2007 Elsevier B.V. All rights reserved.