Table 5. Correlation analyses of various parameters and FeNO levels.

Parameters	FeNO
	r	P
ACOS severity	0.695	< 0.001
FEV1%pred, %	−0.777	< 0.001
FEV1/FVC, %	−0.430	< 0.001
IC/TLC, %	−0.304	< 0.001
RV/TLC, %	0.289	0.001
pH	−0.466	< 0.001
PaO2, mmHg	−0.328	< 0.001
PaCO2, mmHg	0.468	< 0.001
Total serum IgE level, IU/mL	0.726	< 0.001
Induced sputum EOS%	0.578	< 0.001
Plasma SP-A	0.215	0.015
Plasma sRAGE	−0.354	< 0.001
Sputum MPO	0.531	< 0.001
Sputum NGAL, mg/L	0.590	< 0.001
ACT scores	−0.603	< 0.001
CAT scores	0.647	< 0.001

ACOS = asthma-chronic obstructive pulmonary disease overlap syndrome, COPD = chronic obstructive pulmonary disease, ACT = Asthma Control Test, CAT = COPD Assessment Test, MPO = sputum myeloperoxidase, NGAL = sputum neutrophil gelatinase-associated lipocalin, sRAGE = plasma soluble receptor for advanced glycation end products, SP-A = plasma surfactant protein A, EOS = induced sputum eosinophil counts, FEV1%pred = percentage of forced expiratory volume in 1 second (FEV1) to predicted value, FEV1/FVC = the ratio of FEV1 to forced vital capacity, IC/TLC = ratio of inspiratory capacity to total lung capacity, RV/TLC = ratio of residual volume to total lung capacity, FeNO = fractional exhaled nitric oxide, PaO₂ = arterial oxygen partial pressure, PaCO₂ = partial pressure of carbon dioxide in artery, IgE = immunoglobulin E.