1H NMR spectroscopic identification of non-invasive biomarkers of acute rejection and delayed graft function in renal transplantation

Delayed graft function (DGF) and acute rejection (AR) are complications after renal transplantation. It is impossible to differentiate between these clinically. Renal biopsy is the gold standard for diagnosis but is invasive and associated with complications. We aimed to identify early biomarkers, of DGF and AR in renal transplantation, which could lead to a diagnostic test that has no morbidity or mortality associated with its use. In total 163 from twenty-four patients using blood samples over several different pre and post-operative time-points were analysed. Plasma was extracted and analysed by 1H nuclear magnetic resonance spectroscopy (NMR). Spectra were interrogated using multivariate statistics, namely Principal component analysis (PCA) to reveal metabolites whose concentration varied as a function of kidney status. High performance liquid chromatography (HPLC) was used to validate and analyse molecules seen in the NMR studies. Until the third post-operative day, no differences were observed in the plasma metabolic profile of patients with DGF or AR in the NMR studies. From day four onwards molecules, trimethylamine-N-oxide and creatinine were found to vary in concentration across the patient groups in a way that correlated with the transplant outcome. In conclusion biomarkers exist in plasma which permit the discrimination between patients with DGF and AR, from day four following renal transplantation. These biomarkers are accessible, relatively non-invasive and without the morbidity associated with biopsy. A combination of these biomarkers presents the possibility of the development of a clinical diagnostic to improve clinical outcome.