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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

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

  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
  1. 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