Subgroup analysis of the association between GSTT1 null genotype and lung cancer risk.

¤: geographical locations of China were divided into 7 parts: Northeast of China (Jilin province, Liaoning province, Heilongjiang province), North China (Beijing city, Tianjin city, Heber province, Shanxi Province (Taiyuan), Inner Mongolia), East China (Shanghai city, Anhui province, Jiangxi province, Jiangsu province, Zhejiang province, Fujian province, Shandong province,Taiwan), Central China (Henan province, Hubei province, Hunan province), South China (Guangdong province, Hainan province, Guangxi Zhuang Autonomous Region, Hongkong), Southwest of China (Chongqing City, Guizhou province, Sichuan Province, Yunnan Province, Tibet), Northwest of China (Shanxi province (Xi'an), Gansu province, Ningxia Hui Autonomous Region, Xinjiang Uyghur autonomous region).M: model of meta-analysis; R: random-effects model; F: fixed-effects model.PH: p value of heterogeneity test. PE:p value ofEgger's test. POR: PP = 0.000 and the P less than 0.001. @: p values could not be calculated.NA: not available.