TABLE 1

Spirometry results and proportion of children with spirometry data below the lower limit of normal (LLN) or above the upper limit of normal (ULN)

	Boys	*GLI versus* Zapletal**	Girls	*GLI versus* Zapletal**	*Boys versus* girls p-value**^#
Subjects n	215		227
Age	8.4±3.2		8.3±3.3
Children aged <6 years	31.6		32.2
Height cm	131.2±19.7		129.5±19.8
BMI kg·m⁻²	17.2±3.1		17.0±2.8
BMI z-score^¶	0.37±1.28		0.41±1.30
Mean z-scores
GLI
FVC	0.19**±0.94	<0.001	0.18**±0.97	<0.001	0.87
FEV₁	0.31***±0.98	<0.001	0.30***±1.03	<0.001	0.90
FEV₁/FVC	0.11±0.84**	0.001	0.09±0.89*	<0.001	0.91
Zapletal [3, 4]
FVC	0.44*±1.61*		0.35*±1.37*		0.55
FEV₁	0.67*±1.61*		0.56*±1.55*		0.50
FEV₁/FVC	0.28±1.32*		0.63*±1.62*		0.021
Distribution of z-scores	<LLN⁺	>ULN^§	<LLN⁺	>ULN^§	*Boys versus* girls p-value**
GLI
FVC	1.0	6.2	2.0	7.4	0.71
FEV₁	2.2	7.6	3.1	11.3	0.37
FEV₁/FVC	1.1	2.7	4.6	4.6	0.067
Zapletal [3, 4]
FVC	9.2	23.1	5.9	16.2	0.06
FEV₁	6.1	29.3	6.8	22.2	0.27
FEV₁/FVC	7.6	14.6	6.7	24.2	0.061

Data are presented as mean z-scores±sd or %, unless otherwise stated. BMI: body mass index; FVC: forced vital capacity, FEV₁: forced expiratory volume in 1 s. ^#: comparisons of z-score difference performed by Student's t-test. Comparison of proportions of subjects relative to the LLN and ULN were performed by Chi-squared test or Fisher's exact test except when observed frequencies were <5. Means were compared to 0 using paired Student's t-tests and sds were compared to 1 using Chi-squared tests for variance; ^¶: Rolland-Cachera et al. [9]; ⁺: <−1.645 z-score value ; ^§: >1.645 z-score value. *: p<0.05; **: p<0.01; ***: p<0.001.