title: Preanalytical aspects and sample quality assessment in metabolomics studies of human blood.
abstract: BACKGROUND
  Metabolomics is a powerful tool that is increasingly used in clinical research. Although excellent sample quality is essential, it can easily be compromised by undetected preanalytical errors. We set out to identify critical preanalytical steps and biomarkers that reflect preanalytical inaccuracies.
  
  
  METHODS
  We systematically investigated the effects of preanalytical variables (blood collection tubes, hemolysis, temperature and time before further processing, and number of freeze-thaw cycles) on metabolomics studies of clinical blood and plasma samples using a nontargeted LC-MS approach.
  
  
  RESULTS
  Serum and heparinate blood collection tubes led to chemical noise in the mass spectra. Distinct, significant changes of 64 features in the EDTA-plasma metabolome were detected when blood was exposed to room temperature for 2, 4, 8, and 24 h. The resulting pattern was characterized by increases in hypoxanthine and sphingosine 1-phosphate (800% and 380%, respectively, at 2 h). In contrast, the plasma metabolome was stable for up to 4 h when EDTA blood samples were immediately placed in iced water. Hemolysis also caused numerous changes in the metabolic profile. Unexpectedly, up to 4 freeze-thaw cycles only slightly changed the EDTA-plasma metabolome, but increased the individual variability.
  
  
  CONCLUSIONS
  Nontargeted metabolomics investigations led to the following recommendations for the preanalytical phase: test the blood collection tubes, avoid hemolysis, place whole blood immediately in ice water, use EDTA plasma, and preferably use nonrefrozen biobank samples. To exclude outliers due to preanalytical errors, inspect the biomarker signal intensities reflecting systematic as well as accidental and preanalytical inaccuracies before processing the bioinformatics data.
authors: CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
authors: Peiyuan
authors: P
authors: Yin
authors: Andreas
authors: A
authors: Peter
authors: Holger
authors: H
authors: Franken
authors: Xinjie
authors: X
authors: Zhao
authors: Sabine S
authors: SS
authors: Neukamm
authors: Lars
authors: L
authors: Rosenbaum
authors: Marianna
authors: M
authors: Lucio
authors: Andreas
authors: A
authors: Zell
authors: Hans-Ulrich
authors: HU
authors: Häring
authors: Guowang
authors: G
authors: Xu
authors: Rainer
authors: R
authors: Lehmann
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D002853:Chromatography, Liquid; D006461:Hemolysis; D006801:Humans; D055442:Metabolome; D055432:Metabolomics / Q000379:methods* / Q000592:standards; D025341:Principal Component Analysis; D011786:Quality Control; D013048:Specimen Handling / Q000379:methods / Q000592:standards*; D053719:Tandem Mass Spectrometry