Background: We previously found differences in the minor allele frequency (MAF) of single-nucleotide polymorphisms (SNPs) in transmembrane protein 196 (TMEM196) between 995 patients with aspirin-tolerant asthma (ATA) and 141 asthmatic patients with NSAID-exacerbated respiratory disease (NERD). In this study, we statistically analyzed the distributions of the genotypes and haplotypes of these SNPs to determine the exact association between TMEM196 genetic variants and the risk for NERD.
Materials and methods: Lewontin's D' and r values were used to measure linkage disequilibrium between the biallelic loci having MAFs more than 0.05, and haplotypes were inferred using the PHASE algorithm (version 2.0). The genotype distribution was analyzed by logistic regression models using age of onset, smoking status (nonsmoker=0, ex-smoker=1, smoker=2), and BMI as covariates. Regression analysis of the association between SNPs and the risk of NERD was analyzed using SPSS version 12.0 and PLINK version 1.9.
Results: The MAF of rs9886152 C>T was significantly lower in NERD than in ATA [24.8 vs. 34.0%, odds ratio=0.64 (0.48-0.85), P=2.07×10, Pcorr=0.048]. The rate of the rs9886152 C>T minor allele was significantly lower in NERD than in ATA [44.0 vs. 56.4% in the codominant model, P=0.002, Pcorr=0.049, odds ratio=0.64 (0.48-0.85)]. An additional three SNPs (rs9639334 A>G, rs9638765 A>G, and rs2097811 G>A) showed similar associations with the risk of NERD. NERD patients had lower frequencies of the rs9639334 A>G minor allele (51.1 vs. 64.4%, P=0.002, Pcorr=0.043), rs9638765 A>G (49.7 vs. 64.2%, P=0.001, Pcorr=0.017), and rs2097811 G>A (51.1 vs. 64.5%, P=0.002, Pcorr=0.04) compared with ATA patients. Patients homozygous for the minor alleles of the four SNPs showed significantly less of an aspirin-induced decrease in forced expiratory volume in one second compared with those homozygous for the common alleles (P=0.003-0.012).
Conclusion: The minor alleles of the four SNPs in TMEM196 may exert a protective effect against the development of NERD and may be useful genetic markers to predict the risk of NERD.