Systematic review and meta-analysis of the association between C-746T and C-703T polymorphisms of the interleukin-5 gene and asthma

Abstract

Background: Asthma is a common disease with a complex risk architecture including both genetic and environmental factors. A number of studies have identified the association between interleukin (IL)-5 C-746T and C-703T polymorphisms and asthma risk, however, the results still remain inconclusive. The objective of the present study was to identify the effect of IL-5 polymorphisms in asthma susceptibility. Methods: PubMed and Google Scholar databases were searched. The odds ratio (OR) with its 95% confidence interval (CI) was employed to calculate the effect and strength of association in the random-effects model or fixed-effects model. Results: A total of 4 case–control and 2 cross-sectional studies were screened out, including 1499 asthma patients and 3766 controls. Two single-nucleotide polymorphisms of the IL-5 gene were identified. Our results detected a no significant association between IL-5 C-746T polymorphisms and asthma risk in the total population (CC genotype showed OR = 0.82, 95% CI = 0.67–1.00, P = 0.05, I2 = 0%; CT genotype showed OR = 0.94, 95% CI = 0.78–1.13, P = 0.50, I2 = 24%; and TT genotype showed OR = 0.85, 95% CI = 0.64–1.13, P = 0.27, I2 = 0%) while a significant association between IL-5 C-703T polymorphisms and asthma in children according to review results. Conclusion: The meta-analysis findings suggest a lack of direct association between the IL-5 C-746T polymorphism and asthma and found that C-703T polymorphisms of the IL-5 gene might contribute to asthma risk. Future well-designed case–control studies with a large population and more ethnicities are still needed to estimate the association.