This study was divided into several parts: (1) Selection of 8 lncRNAs from previous published studies in comparisons of GC case and control tissues; (2) Test-scale analyses in tissue and plasma using qRT-PCR in order to validate the expression of selected candidates; (3) Validation of lncRNA stability and correlation with blood cells; (4) large-scale analysis of validating of plasma H19 levels by comparing 70 pairs of GC patients and 26 pairs of dysplasia patients; (5) Evaluation of whether plasma H19 levels reflect tumor dynamics (Fig. 1). Here, H19 is linked to gastric cancer.