Citrate NMR peak irreproducibility in blood samples after reacquisition of spectra

Background In our metabolomics studies we have noticed that repeated NMR acquisition on the same sample can result in altered metabolite signal intensities. Aims To investigate the reproducibility of repeated NMR acquisition on selected metabolites in serum and plasma from two large human metabolomics studies. Methods Two peak regions for each metabolite were integrated and changes occurring after reacquisition were correlated. Results Integral changes were generally small, but serum citrate signals decreased significantly in some samples. Conclusions Several metabolite integrals were not reproducible in some of the repeated spectra. Following established protocols, randomising analysis order and biomarker validation are important.