J Mass Spectrom Adv Clin Lab. 2023 Apr;28 35-46
The emerging disciplines of lipidomics and metabolomics show great potential for the discovery of diagnostic biomarkers, but appropriate pre-analytical sample-handling procedures are critical because several analytes are prone to ex vivo distortions during sample collection. To test how the intermediate storage temperature and storage period of plasma samples from K3EDTA whole-blood collection tubes affect analyte concentrations, we assessed samples from non-fasting healthy volunteers (n = 9) for a broad spectrum of metabolites, including lipids and lipid mediators, using a well-established LC-MS-based platform. We used a fold change-based approach as a relative measure of analyte stability to evaluate 489 analytes, employing a combination of targeted LC-MS/MS and LC-HRMS screening. The concentrations of many analytes were found to be reliable, often justifying less strict sample handling; however, certain analytes were unstable, supporting the need for meticulous processing. We make four data-driven recommendations for sample-handling protocols with varying degrees of stringency, based on the maximum number of analytes and the feasibility of routine clinical implementation. These protocols also enable the simple evaluation of biomarker candidates based on their analyte-specific vulnerability to ex vivo distortions. In summary, pre-analytical sample handling has a major effect on the suitability of certain metabolites as biomarkers, including several lipids and lipid mediators. Our sample-handling recommendations will increase the reliability and quality of samples when such metabolites are necessary for routine clinical diagnosis.
Keywords: 1-AG, 1-arachidonoyl glycerol; 1-LG, 1-linoleoyl glycerol; 2-AG, 2-arachidonoyl glycerol; 2-LG, 2- linoleoyl glycerol; ACN, acetonitrile; AEA, arachidonoyl ethanolamide; BHT, 2,6-di-tert-butyl-4-methylphenol; CAR, carnitine; EC, endocannabinoid; FC, fold change; FT, freezing temperature/storage in ice water; HETE, hydroxyeicosatetraenoate; HRMS, high-resolution mass spectrometry; IRB, Institutional Review Board; IS, internal standard; K3EDTA plasma sampling; K3EDTA, tripotassium ethylenediaminetetraacetic acid; LC, liquid chromatography; LEA, linoleoyl ethanolamide; LLE, liquid–liquid extraction; LLOQ, lowest limit of quantification; LPA, lysophosphatidic acid; LPC O, lysophosphatidylcholine-ether; LPC, lysophosphatidylcholine; LPE, lysophosphatidylethanolamine; LPG, lysophosphatidylglycerol; LPI, lysophosphatic inositol; Lipidomics; MS/MS, tandem mass spectrometry; MTBE, methyl tertiary-butyl ether; MeOH, methanol; Metabolomics; OEA, oleoyl ethanolamide; PBS, phosphate-buffered saline; PC, phohsphatidylcholine; PE, phosphotidylethanolamine; PEA, palmitoyl ethanolamide; PI, phosphatidylinositol; Pre-analytics; QC, quality control; REC, Research Ethics Committee; RT, room temperature; Ref, reference sample; SEA, stearoyl ethanolamide; SPE, solid-phase extraction; STD, calibration standard; Sampling protocol; VEA, vaccenic acid ethanolamid; WB, whole blood