Reliability and validity of two self-administered questionnaires for screening restless legs syndrome in population-based studies.
BACKGROUND
A reliable and valid questionnaire for screening restless legs syndrome (RLS) is essential for determining accurate estimates of disease frequency. In a 2002 NIH-sponsored workshop, experts suggested three mandatory questions for identifying RLS in epidemiologic studies. We evaluated the reliability and validity of this RLS-NIH questionnaire in a community-based sample and concurrently developed and evaluated the utility of an expanded screening questionnaire, the RLS-EXP.


METHODS
The study was conducted at Kaiser Permanente of Northern California and the Stanford University Sleep Clinic. We evaluated test-retest reliability in a random sample of subjects with prior physician-assigned RLS (n=87), subjects with conditions frequently misclassified as RLS (n=31), and healthy subjects (n=9). Validity of both instruments was evaluated in a random sample of 32 subjects, and in-person examination by two RLS specialists was used as the gold standard.


RESULTS
For the first three RLS-NIH questions, the kappa statistic for test-retest reliability ranged from 0.5 to 1.0, and sensitivity and specificity was 86% and 45%, respectively. For the subset of five questions on RLS-EXP that encompassed cardinal features for diagnosing RLS, kappas were 0.4-0.8, and sensitivity and specificity were 81% and 73%, respectively.


CONCLUSIONS
Sensitivity of RLS-NIH is good; however, the specificity of the instrument is poor when examined in a sample that over-represents subjects with conditions that are commonly misclassified as RLS. Specificity can be improved by including separate questions on cardinal features, as used in the RLS-EXP, and by including a few questions that identify RLS mimics, thereby reducing false positives.
Popat
Rita A
RA
Dept. of Health Research & Policy, Division of Epidemiology, HRP Redwood Building, Room T209, Stanford University School of Medicine, Stanford, CA 94305-5405, USA. rpopat@stanford.edu
Van Den Eeden
Stephen K
SK
Tanner
Caroline M
CM
Kushida
Clete A
CA
Rama
Anil N
AN
Black
Jed E
JE
Bernstein
Allan
A
Kasten
Meike
M
Chade
Anabel
A
Leimpeter
Amethyst
A
Cassidy
John
J
McGuire
Valerie
V
Nelson
Lorene M
LM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D015203:Reproducibility of Results; D012148:Restless Legs Syndrome / Q000175:diagnosis*; D011795:Surveys and Questionnaires / Q000592:standards