title: Analytes related to erythrocyte metabolism are reliable biomarkers for preanalytical error due to delayed plasma processing in metabolomics studies.
abstract: BACKGROUND
  Delaying plasma separation after phlebotomy (processing delay) can cause perturbations of numerous small molecule analytes. This poses a major challenge to the clinical application of metabolomics analyses. In this study, we further define the analyte changes that occur during processing delays and generate a model for the post hoc detection of this preanalytical error.
  
  
  METHODS
  Using an untargeted metabolomics platform we analyzed EDTA-preserved plasma specimens harvested after processing delays lasting from minutes to days. Identified biomarkers were tested on (i) a test-set of samples exposed to either minimal (n=28) or long delays (n=40) and (ii) samples collected in a clinical setting for metabolomics analysis (n=141).
  
  
  RESULTS
  A total of 149 of 803 plasma analytes changed significantly during processing delays lasting 0-20h. Biomarkers related to erythrocyte metabolism, e.g., 5-oxoproline, lactate, and an ornithine/arginine ratio, were the strongest predictors of plasma separation delays, providing 100% diagnostic accuracy in the test set. Together these biomarkers could accurately predict processing delays >2h in a pilot study and we found evidence of sample mishandling in 4 of 141 clinically derived specimens.
  
  
  CONCLUSIONS
  Our study highlights the widespread effects of processing delays and proposes that erythrocyte metabolism creates a reproducible signal that can identify mishandled specimens in metabolomics studies.
authors.affiliation: Dept. of Molecular and Human Genetics, Medical Genetics Laboratory, Baylor College of Medicine, Houston, TX, United States.
authors.forename: Mahim
authors.initials: M
authors.lastname: Jain
authors.affiliation: Metabolon Inc., Durham, NC, United States.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Kennedy
authors.affiliation: Dept. of Molecular and Human Genetics, Medical Genetics Laboratory, Baylor College of Medicine, Houston, TX, United States.
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Elsea
authors.affiliation: Dept. of Molecular and Human Genetics, Medical Genetics Laboratory, Baylor College of Medicine, Houston, TX, United States. Electronic address: marcusm@bcm.edu.
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Miller
mesh_terms: D015415:Biomarkers / Q000097:blood; D001800:Blood Specimen Collection / Q000592:standards*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D055432:Metabolomics / Q000379:methods*; D010865:Pilot Projects; D010949:Plasma / Q000378:metabolism; D013997:Time Factors
chemical_list: D015415:Biomarkers
keywords: Clinical metabolomics; Phlebotomy; Preanalytical error; Quality control; Whole blood stability