Lack of Association between <b><i>MDR1</i></b> G2677T/A Polymorphism and Leukemia Risk: An Updated Meta-Analysis

available. 2 authors examined the retrieved literature independently and disagreement was resolved by consensus. The quality of the included studies was evaluated using the Newcastle-Ottawa Scale. A maximum score of 9 points could be assigned, where studies with 6 or more points were considered high-quality studies. The pooled odds ratios and 95% confidence intervals were used to assess the strength of association. Totally, 9 studies bearing 1,389 cases and 1,823 controls were included in the meta-analysis. Supplemental table 1 (www.karger.com/?DOI=435904) summarizes the main characteristics of the included studies. In overall comparisons, there was no significant association between MDR1 G2677T/A polymorphism and leukemia risk under 4 genetic models. In the stratification analyses by ethnicity, age, leukemia subtype, and control source, no significant association was observed in any subgroup. The main results of quantitative synthesis are listed in supplemental table 2 (www.karger.com/?DOI=435904). Sensitivity analysis was conducted by omission of studies not in HardyWeinberg equilibrium, and the combined results were not statistically significantly changed, which showed the relative stablity and credibility of the results of the present meta-analysis. A funnel plot was applied to evaluate the publication bias and the results showed that all points in the funnel plot were distributed symmetrically, revealing no statistical evidence for publication bias. In this report, we found no significant association between MDR1 G2677T/A polymorphism and the risk for leukemia in the overall population and the stratification analyses. The results of this meta analysis were not in line with the study reported by Yan et al. [5], in which a significant association was found in Asians and Africans and myeloid leukemia, suggesting that G2677T polymorphism might be a protective factor in the susceptibility to myeloid leukemia. Our results are more convincing because of the relatively lager sample size. However, some limitations should be kept in mind. First, subgroup analyses could not be conducted in Africans and mixed population due to the limited number of