INTRODUCTION Lung cancer is the most commonly diagnosed cancer worldwide and is the leading cause of cancer death. Smoking is a major contributor to the pathogenesis of lung cancer. Cytochrome P450 2A6 (CYP2A6) is responsible for the metabolic activation of most tobacco carcinogens. CYP2A6 genetic polymorphism can cause variations in the human metabolism of xenobiotics. We performed this meta-analysis to determine the association between whole-gene CYP2A6 deletion polymorphism (CYP2A6*4) and lung cancer risk. METHODS The PubMed, SAGE, Science Direct, the Cochrane Library and Ovid databases were searched for observational studies before October 2018. Methodological quality was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS). RESULTS Nine case-control studies involving 4385 lung cancer cases and 4142 controls were included in the analysis. The random-effects model was used to combine results from individual studies. The pooled odds ratio was 0.39 (95% CI: 0.27-0.56). There was no heterogeneity across studies (χ 2 =2.49, p=0.96, I 2 =0%). CONCLUSIONS Current evidence from the case-control studies suggests that the CYP2A6 whole-gene deletion polymorphism decreases the risk of lung cancer. Further research is needed to identify any potential confounding factors that may impact this association.

Background and Aim: Leptospirosis is a zoonotic disease responsible for high morbidity worldwide. This review is intended to identify other possible animal reservoirs of Leptospira spp. within human surroundings, which may improve the prevention and control of the disease.Methods: A systematic search was performed for the relevant titles, abstracts and keywords in PubMed, Scopus and Google Scholar in March 2018 based on the PICO strategy; which returned 1226 studies. Screening of abstracts had shortlisted 71 studies and data extraction was conducted for 15 studies which had been accepted after review of the full text. Only studies done in South-East Asia were considered. Meta-analysis of the accepted studies was done to compute the composite prevalence of each animal group using random effects model. Results:The articles were analysed from the viewpoint of the study settings and the prevalence of Leptospira spp. in types of animal with the animals being grouped into five major groups, based on taxonomy and likelihood of human contact. It was found that all animal groups have statistically significant value of pooled prevalence, with a range between 8.17% (95% CI: 4.80% -12.39%) for sheep and goats, to as high as 27.28% (95% CI: 1.24% -69.69%) for carnivores. The prevalence for other animal groups are 17.95% (95% CI: 7.77% -31.18%) for rodents, 19.24% (95% CI: 10.65% -29.65%) for pigs, and 24.90% (95% CI: 15.45% -35.71%) for ruminants. Conclusion:Meta-analysis showed that other groups of animals, particularly carnivores, pigs, and large ruminants are just as culpable as rodents in being the reservoir for Leptospira spp. These other groups of animals may also play a vital role in the transmission and overall dynamics of human leptospirosis.