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Table 2 Quality of included studies

From: Association between prodynorphin gene polymorphisms and opioid dependence susceptibility: a meta-analysis

Item/Study Nagaya et al. 2018 [13] Hashemi et al. 2018 [14] Clarke et al. 2012 [15] Wei et al. 2011 [16] Jia et al. 2010 [17] Clarke et al. 2009 [18] Yuanyuan et al. 2018 [12]
Adequate definition of cases
Representativeness of cases
Selection of control subjects
Definition of control subjects
Control for important factor or additional factor
Exposure assessment
Same method of ascertainment for all subjects
Non-response rate
  1. , a star given; , a star not given