Objective To assess the value of triggering receptor expressed on myeloid cells-1(TREM-1) in the diagnosis of pneumonia.Methods A systematic review was conducted in Medline,Embase,Cochrane Library,Chinese Bio-medicine Database,and China Hospital Knowledge Database to identify relevant studies on evaluation of TREM-1 in the diagnosis of pneumonia.The methodological quality of each study was assessed by QUADAS.Statistical analysis was performed by employing Meta-Disc 1.4 software.Heterogeneity of the included articles was evaluated for selecting proper effect model to calculate pooled sensitivity,specificity,positive likelihood ratio,negative likelihood ratio,diagnostic odds ratio and 95% CI.Summary receiver operating characteristic(SROC) curve was made and the area under the curve(AUC) was calculated.Results Nine studies with 889 samples met the inclusion criteria for present analysis.The summary estimates for TREM-1 in the diagnosis of pneumonia: sensitivity 0.74(95% CI 0.70,0.78),specificity 0.68(95% CI 0.63,0.72),positive likelihood ratio 2.67(95% CI 1.66,4.28),negative likelihood ratio 0.34(95% CI 0.20,0.57),diagnostic odds ratio 10.76(95% CI 3.89,29.69),and the AUC of SROC was 0.84.Conclusion TREM-1 plays a role in the diagnosis of pneumonia,while the results of TREM-1 assays should be interpreted in parallel with clinical symptoms and other test results.