Plasma Proteome Stability at the Time of Sudden Cardiac Arrest: Implications for Biomarker Studies in Post-Resuscitation Survival

Plasma serves as a crucial source of circulating protein biomarkers for advancing resuscitation strategies in sudden cardiac arrest (SCA). However, emergency blood collection under the SCA introduces preanalytical variables that may affect proteomic analyses. This study assessed plasma protein stability under blood-handling conditions that simulate real-world first responder scenarios. Blood from four individuals was aliquoted and subjected to different (a) initial storage conditions and (b) delays after collection, simulating first responder blood-handling scenarios. Plasma was analyzed using data-independent acquisition mass spectrometry (DIA-MS) for global proteomics and parallel reaction monitoring (PRM-MS) for 16 SCA biomarker candidates. Global proteomic variation was primarily driven by interindividual differences, with less influence from storage conditions or delays. Notably, 87.5% of the candidate biomarkers (14/16) remained stable under ideal storage (4 °C storage immediately after blood collection), and 62.5% (10/16) retained stability even under the "worst-case" conditions (room temperature (RT) storage for 8 h after blood collection) for up to 24 h. However, several proteins lost stability with delayed processing even under ideal storage. Our study highlights the critical importance of processing blood within 24 h of collection and accounting for protein stability to preserve the reliability of biomarkers for improving resuscitation strategies in SCA.