Subgroup analysis
We performed stratified analyses mainly according to age and ethnicity. Subgroup analysis by age indicated a significant relationship amongADRB2 Arg16Gly polymorphism and salbutamol response in adult asthmatics [AG vs. AA: OR=1.894, 95% CI: 1.262-2.843, P =0.002, I2=22.1%, P H=0.274; GG+AA vs. AG: OR=0.597, 95% CI: 0.426-0.837, P =0.003, I2=21.6%, P H=0.277]. However, this relationship disappeared in asthmatic children (Table 2).
When studies were stratified by ethnicity, in Caucasian populations, patients with the AG genotype compared to the GG+AA genotypes showed a good response to salbutamol [GG+AA vs. AG: OR=0.380, 95%CI (0.198, 0.728), P =0.004, I2=25.8%,P H=0.260]. In Asian populations, patients with the AG genotype compared to the AA genotype were associated with a better response to salbutamol [AG vs. AA: OR=1.472, 95%CI (1.018, 2.128), P =0.040, I2=29.0%,P H=0.228] (data not shown). Concerning theADRB2 Gln27Glu polymorphism, no effect on the response to salbutamol was observed when studies were stratified by age or ethnicity under any genetic models (Table 3).