Receiver operating characteristics of impulse oscillometry parameters for predicting obstructive sleep apnea in preobese and obese snorers

Table 3 Sensitivity and specificity values used for detecting patients with and without OSAS, with PPVs and NPVs for the optimal cut-off points for the IOS parameters in the supine position

	Rrs0 (kPa · s · L⁻¹)	Zrs5 (kPa · s · L⁻¹)	R5 (kPa · s · L⁻¹)	Grs (L · kPa⁻¹ · s⁻¹)	Gz (L · kPa⁻¹ · s⁻¹)	X5 supine (kPa · s · L⁻¹)	X5 sitting (kPa · s · L⁻¹)
Cut-off point	0.720	0.640	0.600	1.400	1.500	−0.23	−0.11
Se (%)	62.100	69.900	70.000	62.100	66.900	77.700	73.800
Sp (%)	82.900	72.100	72.100	82.000	72.100	79.400	62.200
PPV (%)	77.200	68.600	69.000	76.200	70.400	76.900	64.400
NPV (%)	70.200	71.600	70.200	70.000	72.100	80.000	71.900
LR+	3.630	2.505	2.590	3.450	2.400	3.770	1.950
LR−	0.457	0.417	0.416	0.462	0.459	0.281	0.421
Pre-test odds	0.920	0.920	0.920	0.920	0.920	0.920	0.920
Post-test probability (LR+)	0.810	0.700	0.706	0.760	0.688	0.776	0.648
Post-test probability (LR−)	0.296	0.278	0.277	0.298	0.297	0.206	0.279

Abbreviations: Se sensitivity, Sp specificity, PPV positive predictive value, NPV negative predictive value, LR+ positive likelihood ratio, LR− negative likelihood ratio. The likelihood ratio is the likelihood that a given test result is expected in a patient with OSAS compared with the likelihood that the same result would be expected in a patient without OSAS, and calculated as sensitivity/(1 – specificity) for LR+, as (1 – sensitivity)/specificity for LR−, pre-test odds = P/(1-P), and post-test probability = pre-test odds*LR. Post-test probabilities for positive or negative tests were calculated according to simplified form of Bayes’ theorem

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