Association between microRNA 21 expression in serum and lung cancer A protocol of systematic review and meta-analysis

Background: Previous studies have reported that microRNA 21 (mRNA 21) has involved in the procedure of lung cancer (LC). However, its conclusions are still unclear. Thus, this study will try to elaborate the association between mRNA 21 expression in serum and LC. Methods: The electronic databases of Cochrane Library, PubMed, EMBASE, Allied and Complementary Medicine Database, WANGFANG database, and China National Knowledge Infrastructure will be retrieved from the inception to the present. All electronic databases will be searched without limitations of language and geographical location. Case-controlled studies reporting the association between mRNA 21 expression in serum and LC will be included. In addition, we will also identify other literature sources to avoid missing potential studies. All study selection, information collection, and study quality assessment will be performed by 2 independent authors. RevMan V.5.3 software and Stata V.12.0 software will be used for data synthesis and analysis. Results: This study will summarize current evidence to investigate the association between mRNA 21 expression in serum and LC. Conclusion: The findings of this study will present comprehensive evidence to determine whether mRNA 21 expression in serum is relevant with LC or not. Systematic review registration: INPLASY202040055.