Fatigue and daytime sleepiness rating scales in myotonic dystrophy: a study of reliability.
OBJECTIVE
To assess the reliability of the Epworth Sleepiness Scale (ESS), Daytime Sleepiness Scale (DSS), Chalder Fatigue Scale (CFS), and Krupp's Fatigue Severity Scale (KFSS) in patients with myotonic dystrophy type 1 (DM1).


METHODS
In total, 27 patients with DM1 were administered the questionnaires on two occasions, with a 2 week interval. Internal consistency and test retest reliability were measured using intraclass correlation coefficients (ICCs), and Cronbach's alpha, Cohen's kappa, and Goodman-Kruskal's gamma coefficients.


RESULTS
Internal consistency of the CFS and KFSS were adequate (alpha > 0.70) but that of the ESS was weak (alpha = 0.24). Both daytime sleepiness and fatigue rating scales showed significant test retest reliability. Test retest reliability for individual items revealed inconsistencies for some ESS and CFS items.


CONCLUSIONS
Reliability of the CFS, DSS, and KFSS was high, allowing their use for individual patients with DM1, but that of the ESS was lower, rendering its current usage in DM1 questionable. Fatigue rating scales such as the KFSS, which are based on the behavioural consequences of fatigue, may constitute a more accurate and comprehensive measure of fatigue severity in the DM1 population.
Laberge
L
L
Unité de recherche clinique, Complexe hospitalier de la Sagamie, Chicoutimi, Québec, Canada, G7H 5H6. laberluc@saglac.qc.ca
Gagnon
C
C
Jean
S
S
Mathieu
J
J
D000328:Adult; D000368:Aged; D002940:Circadian Rhythm; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis* / Q000453:epidemiology*; D005221:Fatigue / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000175:diagnosis* / Q000453:epidemiology*; D012042:Registries; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires