Detecting insomnia in patients with low back pain: accuracy of four self-report sleep measures

Table 4 Prevalence of insomnia, sensitivity, specificity, positive likelihood ratio and negative likelihood ratio values at reported cut-off points and optimal discriminatory cut-off point for each measure

Test	Cut-off point	Insomnia %	Sensitivity	Specificity	LR ^{+ a}	LR ^{- b}
			(95% CI)	(95% CI)	(95% CI)	(95% CI)
Sleep diary	(ICSD-2)^c	25%
Pittsburgh questionnaire^d	>5	67%	100 (83–100)	44 (31–58)	1.8 (1.3 - 2.4)	0
	>6 ^e	63%	100 (83 – 100)	49 (36 – 63)	1.9 (1.5 – 2.5)	0
	>10	24%	50 (27–73)	85 (73–93)	3.28 (2.1 - 5.1)	0.59 (0.3 - 1.2)
Insomnia index^f	>14 ^e	25%	60 (36–81)	86 (75–94)	4.43 (3.1 - 6.4)	0.46 (0.2 - 1.1)
Roland item^g	Yes/no	58%	49 (36 – 63)	80 (56 – 94)	2.46 (0.99 – 6.13)	0.64 (0.46 – 0.89)
Epworth scale^h	>10	23%	76 (63 – 86)	20 (6 – 44)	0.95 (0.73 – 1.24)	1.19 (0.44 – 3.19)

^a Positive likelihood ratio, ^b Negative likelihood ratio, ^c International classification of sleep disorders, ^d Pittsburgh sleep quality index, ^e Maximized cut-off point, ^f Insomnia severity index, ^g Sleep item of the Roland and Morris disability questionnaire, ^h Epworth sleepiness scale.

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