Minimizing preanalytical variation of plasma samples by proper blood collection and handling

Blood samples collected for proteome studies are subject to a variety of preanalytical instability, among which intrinsic proteolysis activities cause a broad spectrum of protein and peptide degradation. This chapter describes two MALDI MS-based methods for plasma peptidomic analyses; a direct MALDI-TOF MS and an LC MALDI-TOF MS. Using these methods, we compared peptides and their time-dependent changes in traditional serum, four plasma samples with different anticoagulants and additives: EDTA-based, citrate-based, or heparin-based, and EDTA-based with protease inhibitors. For minimizing plasma sample instability and preanalytical variation, we suggest using an optimized blood collection device, minimizing the dwell time during blood collection and handling, controlling centrifugation and handling at room temperature, and saving plasma samples for use at most one freeze/thaw cycle. We have optimized our protocol to achieve reproducibility in peptidomic analyses of plasma samples using MALDI-TOF MS by minimizing preanalytical and analytical variability.