GSTM1 and Hematemesis: However, the sensitivities of these signs for high-risk NVUGIB were poor (10.9% for shock, 14.2% for red stool, 50.8%% for red hematemesis, 47.5% for Hb ≤75 g/L), but with high specificity (97.9% for shock, 96.4% for red stool, 85.5% for red hematemesis, 76.7% for Hb ≤75 g/L).