As summarized in table 1, the demographics characteristics of 510 TB cases and 508 unrelated controls were described. The mean age of TB cases was 41.90 ± 14.83 years old including 318 (62.35%) males and 192 (37.65%) females. For healthy controls, the mean age was 41.14 ± 18.42 year old containing 316 (62.20%) males and 192 (37.80%) females. Statistical analysis suggested that the age and gender among all participants were matched. No difference was observed regarding age and gender groups. The p values were 0.469 and 0.961, respectively.
Association between SLC11A1 polymorphism and TB risk
The detailed characteristics of five candidate SNPs in SLC11A1 gene were displayed in table 2. In our study subjects, the MAF of SNPs was more than 0.05. At the same time, all SNPs were accordance with HWE (p > 0.05) among healthy controls. The allele and genotype frequencies distribution of all SNPs between participants were analyzed by χ2 test, and the results were shown in table 3. However, all candidate SNPs of SLC11A1 polymorphism did not present any difference in allele and genotype frequencies among TB patients and healthy controls (all p > 0.05).
Stratified analysis to assess the association between SLC11A1 polymorphism and TB risk
Subsequently, we performed the stratification analysis by age and gender. After analyzing the stratification by age, our results suggested that SLC11A1 rs7608307 “C/T” genotype gene was significantly interacted with improved TB risk in the younger group (age ≤ 41) under the co-dominant genetic models (OR = 1.66, 95% CI = 1.04 – 2.65, p = 0.035). In contrast, rs13062 “A/A” genotype was associated with reduced risk of TB in the old group under the co-dominant genetic model (OR = 0.44, 95% CI = 0.20 – 0.98, p = 0.043) and the recessives genetic model (OR = 0.40, 95% CI = 0.18 – 0.87, p = 0.021) (Table 4). However, there was no significant difference between these remaining SNPs polymorphism and TB susceptibility (p > 0.05), all data was not shown.
The results of stratified analysis on gender demonstrated that a significant correlation between “C/T” and “C/T –T/T” genotypes of rs7608307 and TB risk was observed in males (co-dominant: OR = 1.69, 95% CI = 1.12 – 2.56, p = 0.013; dominant: OR = 1.61, 95% CI = 1.08 – 2.41, p = 0.020, respectively). We also found that the polymorphism of rs7608307 in SLC11A1 gene was interacted with increased TB susceptibility in male under the log-additive genetic model (OR = 1.47, 95% CI = 1.01 – 2.13, p = 0.043). Furthermore, the “C/A” genotype of rs13062 was related to improved TB risk in males (OR = 1.52, 95% CI = 1.10 – 2.12, p = 0.012). For females, the results presented that the “C/C” genotype of rs4674301 was noteworthy increase the risk of TB under the co-dominant genetic model (OR = 3.82, 95% CI = 1.04 – 4.03, p = 0.043) and the recessive genetic model (OR = 3.85, 95% CI = 1.06 – 4.02, p = 0.041). Table 5 displayed all results.