Serum microRNA-21 as a potential diagnostic biomarker for breast cancer: a systematic review and meta-analysis.

Serum microRNA-21 (miR-21) expression has been shown to be significantly up-regulated in breast cancer, which implies that it could be a biomarker to discriminate breast cancer patients from healthy controls. We therefore performed this meta-analysis to assess the diagnostic value of miR-21 for breast cancer. Relevant articles were collected from PubMed, Scopus, Embase, the Cochrane Library, BioMed Central, ISI Web of Knowledge, China National Knowledge Infrastructure, Wan Fang Data and Technology of Chongqing databases, from inception to June 10, 2014 by two independent researchers. Diagnostic capacity of miR-21 for breast cancer was assessed using pooled sensitivity and specificity, diagnostic odds ratio (DOR), area under the summary receiver operating characteristic (AUC) and Fagan's nomogram. Meta-Disc software and Stata SE 12.0 were used to investigate the source of heterogeneity and to perform the meta-analysis. We used six studies with a total of 438 patients and 228 healthy controls in this meta-analysis. The pooled sensitivity, specificity and DOR were 0.79 [95 % confidence interval (CI) 0.66-0.87], 0.85 (95 % CI 0.75-0.91) and 19.46 (95 % CI 8.74-43.30), respectively; positive and negative likelihood ratios were 5 and 0.25, and AUC was 0.89 (95 % CI 0.86-0.91). In addition, heterogeneity was clearly apparent but was not caused by the threshold effect. This meta-analysis suggests that miR-21 is a potential biomarker for early diagnosis of breast cancer with high sensitivity and specificity, and its clinical application warrants further investigation.