Characterization of differences between blood sample matrices in untargeted metabolomics.

Author(s): Denery JR, Nunes AA, Dickerson TJ

Publication: Anal Chem, 2011, Vol. 83, Page 1040-7

PubMed ID: 21175165 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   The purpose of this study was to determine the effects of type of anticoagulant, clotting time, capillary versus venous collection, and analysis of serum versus plasma on the metabolomic profile of blood specimens. In all cases, capillary blood was obtained prior to venipuncture. After collections for the capillary and venous serum comparisons, tubes were allowed to clot, placed on ice for 3-4 h, and centrifuged. For the comparison of plasma with serum, venous blood was collected into heparin or plain tubes, left at room temperature for 30 min, placed on ice for 20 min, carefully aliquoted (without disturbing the clot for serum specimens), and centrifuged. All serum and plasma specimens were aliquoted, flash-frozen, and stored at -80 degrees C until analysis.

   Summary of Findings:

   The average number of features identified in plasma specimens using different anticoagulants was not significantly different, and the authors used heparin for the rest of their analysis. There were also no significant differences between the average number of features identified in serum from blood allowed to clot for 30 min or 4 h before centrifugation. When either the positive or negative ionization modes were used during ESI-TOF-MS analysis, a majority of identified compounds were found to overlap between plasma and serum specimens, but more compounds were identified in serum. With the positive ionization mode, 44 compounds fit the criteria of being identified in 100% of specimens and having a >2-fold change between serum and plasma which was significant (p<0.05). With the negative ionization mode, only 3 compounds fit the criteria. As for the comparison between capillary and venous serum, again, a majority of identified compounds were found to overlap between the two specimen types, and overall, more compounds were identified in capillary specimens. With the application of further restrictive criteria (present in 66% of specimens, >2-fold change, p<0.05), 14 molecules of interest were identified in the positive ionization mode and 9 in the negative ionization mode with differential expression between capillary and venous serum. Importantly, several poly-ethylene glycol polymers fit the restrictive criteria which, the authors hypothesized, were the result of exogenous contamination from skin preparation with alcohol wipes prior to blood collection and were eliminated before the final 14 and 9 of interest were identified. Interestingly, through MS/MS analysis, the authors determined that most of these features of interest in the capillary specimens have the same mass and fragmentation patterns as surfactants, antimicrobials, detergents, and stabilizers.

   Biospecimens

   • Bodily Fluid - Serum
   • Bodily Fluid - Plasma
   • Bodily Fluid - Blood

   Preservative Types

   • Frozen

   Diagnoses:

   • Normal

   Platform:

   Analyte	Technology Platform
   Small molecule	ESI MS
   Peptide	ESI MS

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Aliquots and Components	Blood and blood products	Plasma Serum
   Storage	Storage duration	30 min 4 h
   Biospecimen Acquisition	Anticoagulant	EDTA Heparin Sodium citrate
   ESI MS Specific	Technology platform	Positive ionization mode Negative ionization mode
   Biospecimen Aliquots and Components	Centrifugation	Centrifugation delays investigated
   Biospecimen Acquisition	Anatomical location of blood draw	Capillary Vein

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