Urinary Metabolomics for Noninvasive Detection of Borderline and Acute T Cell–Mediated Rejection in Children After Kidney Transplantation

The goal of this study was to evaluate the utility of urinary metabolomics for noninvasive diagnosis of T cell–mediated rejection (TCMR) in pediatric kidney transplant recipients. Urine samples (n = 277) from 57 patients with surveillance or indication kidney biopsies were assayed for 134 unique metabolites by quantitative mass spectrometry. Samples without TCMR (n = 183) were compared to borderline tubulitis (n = 54) and TCMR (n = 30). Partial least squares discriminant analysis identified distinct classifiers for TCMR (area under receiver operating characteristic curve [AUC] = 0.892; 95% confidence interval [CI] 0.827–0.957) and borderline tubulitis (AUC = 0.836; 95% CI 0.781–0.892), respectively. Application of the TCMR classifier to borderline tubulitis samples yielded a discriminant score (−0.47 ± 0.33) mid-way between TCMR (−0.20 ± 0.34) and No TCMR (−0.80 ± 0.32) (p