Multivariate prediction of diagnosis of patients and healthy controls based on metabolite patterns. (A) Box-and-whisker plot showing the prediction results from cross-validation in the study 1 rheumatoid arthritis (RA) versus control orthogonal projections to latent structures-discriminant analysis (OPLS-DA) model. Negative values correspond to controls and positive values indicate RA diagnoses (see Materials and methods). The blue outlined box denotes the median and 25% and 75% quartiles. The vertical black bars mark the median +1.5 times the interquartile range. (B) Prediction results for discrimination between RA and psoriatic arthritis patients using cross-validation. (C) Prediction results from the follow-up study. The model was built using study 1 data (52 metabolites and nine observations from each group).