High false-positive rate of questionnaire-based restless legs syndrome diagnosis in multiple sclerosis.
OBJECTIVE
Restless legs syndrome (RLS) is diagnosed by self-reported symptoms. Multiple sclerosis (MS) patients have disease-related symptoms which could mimic RLS. This study assessed the: (1) false-positive rate for questionnaire-based RLS diagnosis in MS patients and (2) utility of periodic leg movements during wakefulness (PLMW) on overnight polysomnography (PSG) in identifying true-positive RLS patients.


METHODS
Ambulatory MS patients without known sleep disorders were recruited. Subjects completed the International RLS Study Group (IRLSG) diagnostic questionnaire (IRLDQ) and underwent full overnight PSG. IRLDQ-positive patients underwent clinical evaluation to confirm the diagnosis and completed the RLS severity scale (IRLS).


RESULTS
Seventy-one MS patients (mean age 46.8 ± 10.4 years) were evaluated. Thirty-eight had a positive IRLDQ. RLS diagnosis was confirmed in 22, yielding a false-positive rate of 42% [95% confidence interval (CI) 26-59%], predominantly attributable to paresthesiae (n = 7), and cramps and/or muscle spasms (n = 4). IRLS scores were not significantly different between subjects with confirmed and nonconfirmed RLS. The PLMW index was significantly higher in patients with confirmed RLS (55.4 ± 41.9 vs. 29.7 ± 18.8, p = 0.03). The sensitivity of a PLMW index >70/h for true-positive IRLDQ was 8/22 = 36%, 95% CI: 17.2-59.3, and the specificity was 16/16 = 100%, 95% CI: 79.4-100.


CONCLUSIONS
MS patients have a high false-positive rate of RLS diagnosis using a standardized questionnaire largely attributable to MS-related sensorimotor symptoms. While detailed clinical evaluation is essential for confirming RLS diagnosis, the PLMW index may provide useful adjunctive information.
Respiratory Division and Sleep Laboratory, McGill University Health Centre, 687 Pine Ave. West, Montreal, QC H3A 1A1, Canada.
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Mery
Respiratory Division and Sleep Laboratory, McGill University Health Centre, 687 Pine Ave. West, Montreal, QC H3A 1A1, Canada.
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Kimoff
Respiratory Division and Sleep Laboratory, McGill University Health Centre, 687 Pine Ave. West, Montreal, QC H3A 1A1, Canada.
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Suarez
Department of Medicine, McGill University Health Centre, 687 Pine Ave West, Montreal, QC H3A 1A1, Canada; Department of Epidemiology, Biostatistics & Occupational Health, McGill University, 1020 Pine Ave. West, Montreal, QC H3A 1A2, Canada; Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University, 3650 St. Urbain St, Montreal, QC H2X 2P4, Canada.
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Benedetti
Respiratory Division and Sleep Laboratory, McGill University Health Centre, 687 Pine Ave. West, Montreal, QC H3A 1A1, Canada; Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University, 3650 St. Urbain St, Montreal, QC H2X 2P4, Canada.
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Kaminska
Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University Health Centre, 3801 University St., Montreal, QC H3A 2B4, Canada.
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Robinson
Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University Health Centre, 3801 University St., Montreal, QC H3A 2B4, Canada.
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Lapierre
Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University Health Centre, 3801 University St., Montreal, QC H3A 2B4, Canada.
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Bar-Or
Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University Health Centre, 3801 University St., Montreal, QC H3A 2B4, Canada. Electronic address: daria.trojan@mcgill.ca.
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Trojan
D000328:Adult; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D004185:Disability Evaluation; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis*; D017286:Polysomnography; D011594:Psychometrics / Q000706:statistics & numerical data; D012148:Restless Legs Syndrome / Q000175:diagnosis*; D011795:Surveys and Questionnaires
International Restless Legs Syndrome Study Group questionnaire; Multiple sclerosis; Periodic leg movements; Polysomnography; Restless legs syndrome