Influence of preanalytical sampling conditions on the 1H NMR metabolic profile of human blood plasma and introduction of the Standard PREanalytical Code used in biobanking

Variations in sample collection, processing and storage within the field of clinical metabolomics might hamper its effective implementation. In this study, the impact of relevant preanalytical conditions on the plasma 1H NMR metabolic profile was examined. The biobanking community recently developed a method for coding preanalytical conditions called the Standard PREanalytical Code (SPREC). It is envisaged that SPREC will ultimately identify which samples are fit for a particular analysis, based on prior validation by a panel of experts in the respective field. In an effort to validate SPREC for 1H NMR plasma metabolomics, we have coded the conditions used here, when possible, according to SPREC and evaluated its power to identify preanalytical conditions that affect the plasma 1H NMR metabolic profile. From all preanalytical conditions studied, only prolonged processing delays (3 and 8 h) have a significant impact on the plasma 1H NMR metabolic profile as compared to the reference condition (30 min). Principal component analysis shows a clear systematic shift as a function of increasing processing delay. Nevertheless, the inter-individual variation is clearly much larger than this preanalytical variation, indicating that the impact on multivariate group classification will be minimal. Nonetheless, we recommend to keep the time gap between blood collection and centrifugation similar for all samples within a study. The implementation of SPREC within clinical metabolomics allows for an appropriate sample encoding and exclusion of samples that were subjected to unwanted, interfering preanalytical conditions. Without doubt, it will contribute to the validation of 1H NMR metabolomics in clinical, biobank and multicenter research settings.