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Table 4 Results of backward and forward stepwise logistic regression for predicting OSAS

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

Model construct by backward stepwise method Explanatory variable B S.E. Wald p-values
First step Weight 0.019 0.034 0.326 0.568
BMI 0.067 0.119 0.314 0.575
ERV −0.643 0.553 1.354 0.245
FRC −0.067 0.526 0.016 0.899
Sex 3.526 0.946 13.887 0.000
Zrs5 supine 33.114 11.199 8.742 0.003
R5 supine −31.050 11.438 7.369 0.007
X5 supine −10.980 3.608 9.259 0.002
Constant −10.845 2.790 15.110 0.000
Last step BMI 0.126 0.057 4.831 0.028
ERV −0.658 0.372 3.126 0.077
Sex 3.761 0.847 19.743 0.000
Zrs5 supine 33.474 11.223 8.937 0.003
R5supine −31.493 11.457 7.556 0.006
X5supine −10.814 3.560 9.229 0.002
Constant −11.356 2.282 22.774 0.000
Model construct by forward stepwise method
First step X5 supine −15.475 2.650 34.094 0.000
Constant −3.797 0.627 36.654 0.000
Last step Sex 3.559 0.849 17.572 0.000
Zrs5 supine 34.100 11.483 8.819 0.003
R5supine −31.506 11.723 7.222 0.007
X5supine −11.372 3.583 10.076 0.002
Constant −12.428 2.240 30.784 0.000
  1. Abbreviations: BMI body mass index, ERV expiratory reserve volume, FRC functional residual capacity, Zrs5 respiratory impedance at 5 Hz, R5 respiratory resistance at 5 Hz, X5 respiratory reactance at 5 Hz. Outcome variable is the probability (p) of the presence of OSAS (RDI 15) / absence of OSAS (RDI <15); namely, ln(p/(1-p)