Table 3 Associations between GSTP1 and GSTM1 genotypes and haplotypes with new onset asthma
ModelGenotype and haplotype†No (with asthma/without asthma)HR (95% CI)*p Value§
GSTP1
    JointSNP1(A)150/14741.23 (0.8 to 1.9)0.03
SNP2(G)0.85 (0.6 to 1.2)
SNP3(G)0.54 (0.3 to 0.9)¶
SNP4(T)1.10 (0.6 to 1.9)
    FunctionalSNP1(A)150/14931.40 (1.1 to 1.9)¶0.007
SNP3(G)0.60 (0.4 to 0.8)**
    Haplotype‡TCAC150/14741 (Ref)0.14
ACAC1.33 (0.8 to 2.2)
TGAC0.90 (0.6 to 1.4)
TCGC0.64 (0.3 to 1.2)
ACGT0.76 (0.5 to 1.2)
Other0.97 (0.5 to 1.9)
GSTM1Null152/14721.61 (1.2 to 2.2)**0.004
Joint GSTM1 and GSTP1 model
    GSTP1SNP1(A)144/14531.45 (1.1 to 1.9)¶0.007††
SNP3(G)0.61 (0.4 to 0.8)**
    GSTM1Null1.52 (1.1 to 2.1) ¶
  • *Hazard ratio (HR) and 95% CI adjusted for community of residence and ethnicity. Additive genetic coding was used for all SNPs.

  • †The letter in parentheses represents the variant allele.

  • ‡The sequence of the GSTP1 haplotype is SNP1-SNP2-SNP3-SNP4. Haplotypes with less than 5% frequency in both the ethnic groups were summarised as “Other”.

  • §The p value is derived from the LRT. The LRT was calculated by comparing models with and without the corresponding genetic data.

  • ¶p value <0.05; **p value <0.001.

  • ††This LRT P value was calculated by comparing a model with SNP1 and SNP3 of GSTP1and GSTM1 “null” to one with only GSTM1 “null”. All models were adjusted for ethnicity and community of residence.

  • GST, glutathione-S-transferase; LRT, likelihood ratio test; SNP, single nucleotide polymorphism.