Study objectives: To develop and validate a telephone diagnostic interview (the Johns Hopkins telephone diagnostic interview for restless legs, abbreviated TDI) for diagnosis of the restless legs syndrome (RLS).
Design and methods: Using the International RLS Study Group diagnostic criteria, specific questions were developed reflecting the diagnostic features of RLS. Seventy-five subjects (37 previously diagnosed RLS patients and 38 controls self-reported to be free of RLS) were interviewed by three expert interviewers blinded to each others' interviews and the patient's clinical status. The interviewers diagnosed each subject based on responses to the TDI.
Results: The interviewers overall correctly diagnosed 72 of 75 individuals. Minimum interviewer sensitivity and specificity were 97 and 92%, respectively. The intraclass correlation coefficient (ICC) was used to quantify inter-rater reliability for the three interviewers. The ICC for diagnosis was 0.95. The ICC calculated on other key items in the interview exceeded 0.80 in all cases. The patients were predominantly older individuals with long-standing RLS; 19 of them scored at the highest level of severity on the Johns Hopkins Restless Legs Severity Scale (JHRLSS). The interviewers had more difficulty with assessing the controls accurately, some of whom were probably incorrectly self-categorized as not having RLS.
Conclusions: The TDI is a sensitive, specific, and reliable instrument for diagnosing RLS by experienced interviewers in a brief, anonymous telephone encounter.