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. 2005 Dec 5:3:79.
doi: 10.1186/1477-7525-3-79.

The reliability, validity and responsiveness of the Restless Legs Syndrome Quality of Life questionnaire (RLSQoL) in a trial population

Linda Abetz  1 , Robert Arbuckle, Richard P Allen, Elena Mavraki, Jeffrey Kirsch
Affiliations

The reliability, validity and responsiveness of the Restless Legs Syndrome Quality of Life questionnaire (RLSQoL) in a trial population

Linda Abetz et al. Health Qual Life Outcomes. .

Abstract

Background: The aim of this study was to determine the reliability, validity and responsiveness of the Restless Legs Syndrome Quality of Life questionnaire (RLSQoL) in a clinical trial setting.

Methods: Two matching, placebo-controlled, multinational studies assessing the effectiveness and safety of ropinirole for treating moderate-to-severe Restless Legs Syndrome (RLS) formed the basis of this psychometric assessment. Validity and reliability were assessed using baseline data. Responsiveness was determined using longitudinal data collected at baseline and 12 weeks.

Results: A total of 547 subjects formed the baseline validation population; 519 were used for assessing responsiveness (n = 284/263 and 271/248 for both studies, respectively). Construct validity assessment confirmed that an overall life impact score could be calculated. All item-scale correlations were = 0.4, except items 1 (r = 0.36) and 5 (r = 0.35) in one study. Floor and ceiling effects were minimal. Cronbach's alpha values were 0.82 and 0.87, respectively, confirming internal consistency reliability. Correlations with the International Restless Legs Syndrome Study Group's severity rating scale (International Restless Legs Scale; IRLS) were moderate (r = -0.68 and -0.67, respectively; p < 0.0001). The RLSQoL was able to discriminate between levels of sleep problems (p < 0.0001) and between levels of global health status determined by a Clinical Global Impression of severity (CGI-S) (p < 0.0001). Responsiveness was demonstrated by significant differences in overall life impact change scores between CGI improvement levels after 12 weeks (p < 0.0001).

Conclusion: The RLSQoL is a valid, reliable and responsive measure of quality of life for patients with RLS, in a clinical trial setting where group comparisons are anticipated.

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Figures

Figure 1
Figure 1
Known groups validity. RLSQoL overall life impact scores by mild, moderate and severe sleep problems. p < 0.0001 for comparisons of RLSQoL overall life impact scores among sleep problems severity groups defined by taking tertile scores for the Sleep Problems Index II in TREAT RLS 1 and 2 (Kruskall-Wallis test). RLSQoL = RLS Quality of Life questionnaire.
Figure 2
Figure 2
Clinical validity. Comparison of RLSQoL overall life impact scores at baseline among CGI-S groups. CGI-S subgroups 1–2 include normal, not at all ill and borderline ill patients; subgroups 3–5 include mild, moderate, and markedly ill patients; and subgroups 6–7 include severely ill, and the most extremely ill patients. p < 0.0003 (Kruskall-Wallis test comparing all three subgroups) and p < 0.000.1 (Mann-Whitney-Wilcoxon test comparing subgroups 3–5 with 6–7) for comparisons of RLSQoL overall life impact scores among collapsed CGI-S subgroups in both TREAT RLS 1 and 2; p = not significant (Mann-Whitney-Wilcoxon test comparing subgroups 1–2 with 3–5). RLSQoL = RLS Quality of Life questionnaire. CGI-S = Clinical Global Impression 'Severity of Illness'.
Figure 3
Figure 3
Responsiveness. Effect sizes as a measure of the change in RLSQoL overall life impact change scores between baseline and week 12, by CGI-I scores at week 12. p < 0.0001 for comparisons of the change in RLSQoL overall life impact scores among CGI-I groups in both TREAT RLS 1 and 2 (Kruskall-Wallis test). The sample size of n = 1 in the 'worsened' group in TREAT RLS 2 meant that effect sizes could not be calculated. RLSQoL = RLS Quality of Life questionnaire. CGI-I = Clinical Global Impression 'Improvement'.
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References

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