Fig. 1

Formate classifier. a Schematic representation of a standard case-control study to identify and validate disease metabolite biomarkers. b Box plots of serum formate levels across healthy controls (H), HER2+ breast cancer (BC) and non-small cell lung cancer (LC) samples. Each point represents a sample, the error bars indicate the range excluding the lowest 5% and highest 5% values, boxes the range excluding the lowest 25% and highest 25% values, and the line within the box the median. Asterisk/double asterisks denote a significant difference of 10⁻³/10⁻⁶ relative to healthy controls (−), two-tailed t test with unequal variance. c, d Volcano plots reporting the statistical significances vs fold change of metabolite levels relative to the healthy controls, in BC (c) and LC (d). Each point represents a metabolite and selected metabolites are indicated by their abbreviated name. e ROC plot for the formate-based classifier (brown line), together with the FPR and TPR obtained from cross-validations not corrected (CV) and accounting (CV corrected) for obesity incidence The symbol reports the median and the error bars the observed range excluding the 5% lowest and largest values