Figure 1

PCA scores plots for (a) positive and (b) negative ion mode data of healthy participants from Thailand and United Kingdom. OPLS-DA scores plots showing group separation for both (c) positive and (d) negative ion mode data and corresponding permutation tests for (e) positive and (f) negative ion mode data. (a) R2X = 30% and Q2X = 14% from 2 PC model; (b) R2X = 26% and Q2X =  − 4% from 2 PC model; (c) R2Y = 95%, R2X = 21% and Q2Y = 87%, from one predictive and one orthogonal components model; (d) R2Y = 93%, R2X = 17% and Q2Y = 79%, from one predictive and one orthogonal components model; (e) Permutation test—positive mode CV-ANOVA =  < 0.001; (f) Permutation test—negative mode CV-ANOVA =  < 0.001.