Fig. 3

Partial least squares discriminant analysis (PLS-DA) score plots (left panel) and statistical validation of the corresponding PLS-DA model by permutation analysis (right panel) based on the ¹H nuclear magnetic resonance spectra of (a) plasma, (b) urine and (c) tissue metabolites obtained from the patients with ankylosing spondylitis (red circles) and from the healthy control subjects and patients with femoral neck fracture (black squares). Principal component 1 (PC1) and PC2 explained (a) 42.1 % and 16.0 %, (b) 39.4 % and 11.3 %, and (c) 51.6 % and 18.7 % of the variables, respectively