Table 2– Characteristics and factors associated with exhaled nitric oxide fraction in healthy Asian children by univariate analyses

Continuous variable	Mean±sd	n	R	p-value
Age yrs	10.2±2.6	661	0.176	<0.001
Anthropometric measurement
Height cm	138.2±14.7	661	0.136	0.001
Weight kg	36.1±13.0	661	0.073	0.062
BMI kg·m⁻²	18.3±3.5	661	-0.015	0.699
Body surface area m²	1.17±0.26	661	0.092	0.018
Pulmonary function
FVC L	2.03±0.65	650	0.102	0.009
FEV₁ L	1.77±0.55	650	0.119	0.002
FEV₁/FVC ratio %	87.7±6.0	650	0.073	0.064
FEF_25–75% L·s⁻¹	2.20±0.74	650	0.125	0.001
FVC % pred	90.5±11.3	650	-0.104	0.008
FEV₁ % pred	89.9±10.3	650	-0.065	0.096
FEV₁/FVC % pred	97.7±6.7	650	0.091	0.020
FEF_25–75% % pred	90.7±19.5	650	0.010	0.796
Total IgE kU·L⁻¹	166.1±391.1	512	0.299	<0.001
Ambient nitric oxide ppb	2.51±2.86	661	0.087	0.026
Ambient temperature °C	23.0±5.9	661	-0.009	0.822

BMI: body mass index; FVC: forced vital capacity; FEV₁: forced expiratory volume in 1 s; FEF_25–75%: forced expiratory flow at 25–75% of FVC; % pred: % predicted; IgE: immunoglobulin E. p-values in bold are significant.