Circulating microRNA-21 as a biomarker for the detection of various carcinomas: an updated meta-analysis based on 36 studies

Cancer is a class of diseases with high mortality rate, characterized by unregulated cell growth. Early diagnosis of cancer is currently the most effective method to prevent cancer development and improve the survival rate of patients. Traditional diagnostic methods such as biopsy usually provoke discomfort and unpleasant experience. Recently, microRNAs (miRNAs) were widely reported to be potential biomarkers to detect cancers without invasiveness. MicroRNA-21 (miRNA-21, miR-21) is one of the most prevalent miRNAs. This meta-analysis aims to make a comprehensive analysis of the potential role of circulating miR-21 as a biomarker in human carcinoma diagnosis. A total of 36 articles involving 2920 cancer patients and 1986 healthy controls with regard to the diagnostic value of the circulating miR-21 for cancer detection were selected from online bibliographic databases. For pooled analysis, the sensitivity, specificity, and other basic characteristics were extracted from the 36 included articles. Then, bivariate random-effects model was selected to gain pooled results. Furthermore, to explore the sources of heterogeneity, we conducted stratified and meta-regression analyses based on different race/sample groups. The pooled characteristics of all included articles were as follows: sensitivity, 0.78 (95 % confidence intervals (CI), 0.73–0.82); specificity, 0.82 (95 % CI, 0.79–0.86); positive likelihood ratio (PLR), 4.4 (95 % CI, 3.6–5.4); negative likelihood ratio (NLR), 0.26 (95 % CI, 0.21–0.33); diagnostic odds ratio (DOR), 17 (95 % CI, 12–24); and area under the curve (AUC), 0.87 (95 % CI, 0.84–0.90). The subgroup analyses results based on different ethnic populations revealed that the diagnostic accuracy of miR-21 tends to be higher in Asian populations than in Caucasian populations. Furthermore, another subgroup analysis performed on sample types suggested that the serum-based specimen used in cancer diagnosis appeared to be more accurate than the plasma-based specimen. Our meta-analysis shows that the circulating miR-21 may be a potential biomarker as diagnostic tool for early-stage cancer diagnosis.