PR of 1H-NMR spectra of tissue specimens. A, scores plot of PCA model based on 26 cases normal mucosae (black triangles) and 89 cases esophageal cancers (red dots). B, scores plot of OPLS-DA model processing based on same samples. C, statistical validation of the corresponding PLS-DA model by permutation analysis (200 times). R2 is the explained variance, and Q2 is the predictive ability of the model. D, scores plot of OPLS-DA prediction model. 80% of samples (training set, normal mucosae =20, esophageal cancer = 71) were applied to construct the model, and then used it to predict the remaining 20% of samples (testing set, normal mucosae =5, esophageal cancer = 18). Green diamonds represent normal mucosae and yellow inverted triangles represent esophageal cancers.