Table 4

 Association of asthma exacerbations and polymorphisms according to BTS treatment step

BTS treatment step*GenotypeExacerbations over previous 6 monthsTotalOR(p value)
NoYes
More asthma exacerbations occurred in association with the Arg16 polymorphism in patients on BTS step 3 treatment, but not in those on BTS treatment steps 1, 2 and 4.
*BTS treatment steps: step 1 = salbutamol according to need; step 2 = step 1 + regular inhaled steroids; step 3 = step 2 + regular inhaled long acting β2 agonist; step 4 = step 3 + oral montelukast.
†p values were calculated by binary logistic regression analysis corrected for age, sex, and exposure to tobacco smoke using a co-dominant model—that is, a gene/dosage effect for the Arg16 variant. Odds ratios are per genotypic step.
Step 1Gly16Gly27 (77%)8 (23%)351.084(p = 0.852)†
Arg16Gly24 (75%)8 (25%)32
Arg16Arg10 (83%)2 (17%)12
Total611879
Step 2Gly16Gly70 (64%)40 (36%)1101.281(p = 0.163)†
Arg16Gly93 (64%)53 (36%)146
Arg16Arg24 (52%)23(49%)47
Total187116303
Step 3Gly16Gly24 (67%)12 (33%)362.168(p = 0.023)†
Arg16Gly24 (56%)19 (44%)43
Arg16Arg4 (31%)9 (69%)13
Total524092
Step 4Gly16Gly13 (48%)14 (52%)271.617(p = 0.249)†
Arg16Gly13 (41%)20 (61%)33
Arg16Arg5 (42%)7 (58%)12
Total31 (44%)41 (57%)72