3.6 Assessment of the diagnostic performance of biomarkers
Univariate ROC curves were generated for each metabolite at each timepoint, and univariate AUROC was calculated to assess the diagnostic performance of each individual metabolite. All AUROC values for early plasma markers were summarized in Figure 7A for C57BL/6 mice and Figure S8A for FVB/N mice. All AUROC values for early urine markers were summarized in Figure 8A for C57BL/6 mice andFigure S9A for FVB/N mice. Metabolites were ranked from highest to lowest univariate AUROC values. Multivariate ROCs were generated to assess the aggregate diagnostic performance of a combination of metabolites, ranging from a combination of the top two highest ranked metabolites to the top 10 and top 15 ranked metabolites for plasma (Figure 7, S8 ) and urine (Figure 8, S9 ), respectively.
An AUROC value ≥ 0.7 is generally considered to be acceptable. When discriminating saline vs. cisplatin treated C57BL/6 mice, plasma creatinine had an AUROC of 0.719 at day 1. Nine plasma metabolites had an AUROC ≥ 0.7 when discriminating saline vs. cisplatin-treated C57BL/6 mice on day 1 (creatine; 0.729, equol 4-sulfate; 0.736, L-acetylcarnitine; 0.944, L-carnitine; 0.944, LysoPC(20:3); 0.875, phenylalanine; 0.917, taurocholic acid; 0.708, trigonelline; 0.785, and tryptophan; 0.826). Eight of the nine metabolites with AUROC ≥ 0.7 on day 1 outperformed plasma creatinine, with the exception of taurocholic acid. In FVB/N mice, plasma creatinine had an AUROC of 0.562 at day 1. Five plasma metabolites in FVB/N mice had an AUROC ≥ 0.7 at day 1 (creatine; 0.773, pyrocatechol sulfate; 0.828, taurine; 0.719, taurocholic acid; 0.891, and trigonelline; 0.891). All 5 metabolites with AUROC ≥ 0.7 on day 1 outperformed plasma creatinine on day 1.
Multivariate ROCs generated for C57BL/6 plasma samples at day 1 revealed a maximum AUROC of 0.877, which was achieved in the ROC curve modeled using the top three ranked metabolites: L-acetylcarnitine, phenylalanine, and LysoPC(20:3) (Figure 7B ). The maximum multivariate AUROC achieved in C57BL/6 urine was 0.545 on day 1, but reached AUROC values of 1 in all combinations of the top two to top 15 metabolites on day 2 (Figure 8B, 8C ). In FVB/N plasma, a peak AUROC of 0.656 was obtained at day 1, whereas AUROC values of ≥ 0.991 were observed on day 2 for all combinations of metabolites (Figure S8B, S8C ). In day 1 FVB/N urine samples, the highest multivariate AUROC value of 0.940 was produced via the combination of all 15 early urine metabolites (Figure S9B ). Diagnostic performance was further improved in day 2 FVB/N urine, with all metabolite combinations yielding an AUROC ≥ 0.953 (Figure S9C ).