Table 1

Difference in FEF_25–75 related to ozone concentration on the day before spirometric testing according to GSTM1 genotype in asthmatic children in Mexico City given antioxidant supplementation or placebo

		All asthmatics			Moderate and severe asthmatics
Group	Subgroup	n*	Coefficient (95% CI)†, ml/s 50 ppb O₃	Percentage (95% CI) change‡ FEF_25–75/50 ppb O₃	n	Coefficient (95% CI), ml/s 50 ppb O₃	Percentage (95% CI) change FEF_25–75/50 ppb O₃
The number of subjects in each group is given. The number of observations is: GSTM1* null (placebo 654, supplement 732), GSTM1 positive (placebo 1065, supplement 1039).
†Results and 95% confidence intervals from generalised estimating equation models adjusted for age, height, use of bronchodilator, respiratory symptoms on the day of the spirometric test, minimum temperature, and time since the beginning of the study. Ozone level is 1 hour maximum. During the observation period the mean (SD)1 hour maximum ozone was 102 (47) ppb (range 12–309). The Mexican standard is 110 ppb.
‡Percentage change from baseline FEF_25–75 for the individual stratum.
§p⩽0.01. All p values were obtained by t test comparing coefficients between the two groups.
¶0.05<p<0.10
Placebo	GSTM1 null	29	−50.5 (−90.1 to−10.9)§	−2.9 (−5.2 to −0.6)§	18	−80.8 (−132.7 to −28.9)§	−4.7 (−7.7 to−1.7)§
	GSTM1 positive	49	−10.5 (−38.7 to 17.7)	−0.6 (−2.1 to 0.9)	17	−34.4 (−75.6 to 6.8)	−1.9 (−4.4 to 0.5)
	Genotype effect		40.0 (−7.5 to 87.5)¶	2.3 (−0.2 to 4.9)¶		46.4 (−20.7 to 113.4)	2.8 (−1.2 to 6.7)
Supplement	GSTM1 null	33	−3.0 (−40.7 to 34.7)	−0.2 (−2.3 to1.9)	21	−7.3 (−54.0 to 39.5)	−0.3 (−3.1 to 2.4)
	GSTM1 positive	47	5.1 (−29.8 to 40.1)	0.3 (−1.6 to 2.2)	26	2.0 (−43.8 to 47.8)	0.1 (−2.4 to 2.6)
	Genotype effect		8.1 (−44.1 to 60.4)	0.5 (−2.4 to 3.3)		9.3 (56.5 to 75.2)	0.4 (−3.2 to 4.1)