RESULTS

Demographic characteristics and laboratory results

The mean age of the total patient group was 46.3 ± 25.9 months (median 46), and the mean age of the control group was 23.9 ± 13.4 months (median 20) (p < 0.001). In the patient group, 37 (36.3%) of the cases were female, and 35 (40.7%) of the patients in the control group were female; (p = 0.534). A comparison of the demographic characteristics and laboratory results of the patient subgroups is shown in Table 1.

Genetic workup with real-time PCR

1. Genotype analysis of the studied SNPs

1a. Comparison of total patient group and controls
The genotypes were grouped as homozygote, heterozygote, or wild. After determining the genotypic distribution, we performed a genetic comparison according to the autosomal recessive inheritance pattern of the ARG1 and ARG genes between the patients, controls, and patient subgroups. There was no difference between the total patient group and the healthy controls in terms of the homozygote genotype of the SNPs in the ARG1 and ARG2 genes (Table 2).
1b. Comparison of patient subgroups
The homozygote cytosine-cytosine (CC) genotype of the ARG1rs2781667T>C SNP in the EW group was significantly lower than for the controls (p = 0.006) [OR (95% CI): 0.26(0.10–0.66)], the MW group (p = 0.002) [OR (95% CI): 0.19(0.06–0.52)], and the asthmatics (p = 0.025) [OR (95% CI): 0.22(0.06–0.75)]. There was no difference in the distribution of the other studied SNPs in the ARG1 and ARG2 genes between the patient subgroups and the controls (Table 2).
1c. Association between the SNP analysis and allergic rhinitis, aeroallergen sensitivity, number of aeroallergens detected as positive in the skin prick test, and tobacco exposure
The homozygote CC genotype of the ARG1 rs2781667T>C SNP was more frequent in patients with AR than in those without AR (49.1% and 21.3%, respectively, p = 0.007) [OR (95% CI): 3.56(1.48–8.56)].
There was no difference in the presence of aeroallergen sensitivity, the number of aeroallergens detected as positive in the skin prick test, tobacco exposure, and homozygote genotype distribution of any SNPs among all the patient groups.

2. Haplotype analysis

2a. Comparison of total patient group and controls
There was a statistically significant difference in terms of ARG 1 haplotype 5 (CT/T/G/T/T/CT) and ARG 1 haplotype 9 (C/T/G/T/T/T) between the healthy controls and the patient group. The frequency of theARG1 haplotype 5 in the patient group was 9.8% and 1.2% in the control group (p = 0.028) [OR (95% CI): 9.23(1.15–73.70)]. The frequency of ARG1 haplotype 9 in the patient group was 2% and 11.6% in the control group (p = 0.016) [OR (95% CI): 0.15(0.03–0.71)]. There was no difference between the patient groups and the controls in terms of other haplotypes in the ARG1 andARG2 genes (see Tables 3A and 3B).
2b. Comparison of patient subgroups
The frequency of the ARG1 haplotype 2 (CT/T/AG/AT/CT/CT) was significantly higher in the EW group than in the healthy control and MW groups (p = 0.041) [OR (95% CI): 2.76(1.13–6.76)] and (p = 0.014) [OR (95% CI): 5.88(1.49–25.0)], respectively. The frequency of haplotype 5 was significantly higher in the EW group than in the controls (p = 0.005) [OR (95% CI): 14.16(1.64–121.93)]. The ARG1 haplotype 4 (C/T/A/A/C/T) was more frequent in the MW, asthmatics, and control groups than in the EW group (p < 0.0001) [OR (95% CI): 7.77(2.54–23.7)], (p = 0.036) [OR (95% CI): 4.31(1.15–16.15)], and (p = 0.030) [OR (95% CI): 3.44(1.20–10.0)], respectively (see Tables 3A, 3B).
2c. Association between SNP analysis and allergic rhinitis, aeroallergen sensitivity, number of aeroallergens detected as positive in the skin prick test, and tobacco exposure
ARG1 haplotype 4 was more frequent in patients with allergic rhinitis than those without allergic rhinitis, 41.8% and 21.3%, respectively (p = 0.046) [OR (95% CI): 2.65(1.10–6.41)].
There was no difference in terms of haplotype distribution and presence of aeroallergen sensitivity, the number of aeroallergens detected as positive in the skin prick test, and tobacco exposure among all the patient groups.