AFP and hepatocellular carcinoma: The 1H-NMR serum spectra of the patients with AFP-negative HCC and NCs were discriminated with the OPLS-DA model, as shown in a score plot (Figure 3a), and the predictive ability was calculated through 7-fold cross-validation (R2Y = 0.848, Q2Y = 0.827, CV-ANOVA p < 0.0001).