PCA broadly distinguishes between inflammatory and non-inflammatory conditions.

<p>PCA scores plot for the model building dataset (Set 1). Most non-inflammatory cases (blue) are associated with positive scores, located in the upper part of the plot. There is more variation in the distribution of the inflammatory cases (yellow) but many associate with negative scores (<b>A</b>). The PCA loadings plot shows that all the measured variables except age underlie the observed scores distribution seen in A (<b>B</b>). Scores of the test set (Set 2) were predicted using the model derived for Set 1. Non-inflammatory conditions, again, cluster mostly in the upper part of the plot (<b>C</b>). Extreme outliers (≥3 SD) in both scores plots belonged to cases of herpes encephalitis and neuroborreliosis.