Modification and validation of a diagnostic questionnaire for restless legs syndrome: Modified-restless legs syndrome diagnostic questionnaire (m-RLS-DQ)

Background: Diagnostic questionnaire that are available for restless legs syndrome does not include items related to RLS mimics and, hence, increases chances of false positive cases. This study aimed at modification and validation of RLS-diagnostic Questionnaire. Methods: During modification, additional items were identified, developed, and subjected to evaluation by experts. Experts were requested to validate the content of each item. Based on their responses, content validity indices (average and universal agreement) were calculated. It was then translated to Hindi and validated in a clinical population that included patients with RLS, somatic symptoms disorder, anxiety, other RLS mimics, and osteoarthritis. In addition, a group of healthy controls was also included. Face, concurrent, and discriminant validities were calculated. Results: Among 209 subjects, nearly 40 subjects had clinical diagnosis of RLS, osteoarthritis, somatic-symptoms-disorder, and anxiety disorder, each. In addition, 16 patients had other RLS mimics (akathisia, varicose veins, BFS, leg-cramps, chronic insomnia) and 30 were healthy controls. After multiple revisions, content validity indices achieved a score of 1 for m-RLS-DQ. Sensitivity and specificity of m-RLS-DQ v. 1.4 for the diagnosis of RLS were 94.9% and 94.1%, respectively. For the diagnosis of RLS, PPV was 78.7%, and NPV was 98.7% with an accuracy of 94.3%. Less than one fourth of participants having chronic insomnia, somatic symptoms disorder, anxiety disorder, and knee osteoarthritis were found to be false positive on m-RLS-DQ; however, none of the healthy controls were found positive on m-RLS-DQ. Concurrent validity with clinical diagnosis of RLS was 0.83 (P < 0.001). Discriminant validity with somatic symptoms disorder was −0.14 (P = 0.03) and with osteoarthritis −0.24 (P < 0.001). Conclusion: m-RLS-DQ is a valid instrument with acceptable psychometric properties, which can be used for the screening as well as diagnosis of RLS in clinical practice and research studies.