Table 5.
OPLS-DA of group membership (CON denoted 0 and FM denoted 1). Regressors used data from spectroscopy and microdialysis (except pain variables from microdialysis) (cf. Table 3 and Table 4). The regression had one predictive component. Only significant variables are shown (i.e., variables with VIP > 1.0 and absolute p(corr) ≥ 0.50).
| Variables | VIP | p(corr) |
|---|---|---|
| Blood flow Erector spinae 140 min | 2.37 | −0.83 |
| Mean Blood flow Erector spinae 140−220 min | 2.27 | −0.81 |
| Blood flow Erector spinae 160 min | 2.23 | −0.80 |
| PCR (mM) | 1.97 | −0.70 |
| PCr/Ptot | 1.94 | −0.69 |
| ATP (mainly ATP; mM) | 1.94 | −0.69 |
| Pi/PCr | 1.82 | 0.65 |
| Pyruvate trapezius 140 min | 1.60 | 0.57 |
| Mean Blood flow Trapezius 140–220 min | 1.57 | −0.55 |
| ATP/PCr | 1.49 | 0.53 |
| Blood flow Trapezius 160 min | 1.42 | −0.50 |
| R2 | 0.26 | |
| Q2 | 0.18 | |
| CV-ANOVA p-value | 0.003 | |
| n | 61 |
VIP and p(corr) are reported for each regressor (i.e., the loading of each variable scaled as a correlation coefficient and therefore standardizing the range from −1 to + 1). The sign of p(corr) indicates the direction of the correlation with the dependent variable (+ = positive correlation; − = negative correlation). Hence, a negative p(corr) indicates lower values for a certain variable in FM in the multivariate context. The four bottom rows report R2, Q2, P-value of the CV-ANOVA, and number of subjects included in the regression (n) from the second OPLS regression (see Statistics for details).