Effect of delayed blood centrifugation on cytokine quantitation in serum and plasma.

Cytokines are critical biomarkers, but their accurate measurement is susceptible to pre-analytical variables. This study investigated the effect of delayed blood processing on the quantitation of eight cytokines (CCL2, CXCL10, IFN-γ, IL-2Ra, IL-6, IL-7, IL-18, TNFα) in matched serum and plasma from healthy volunteers. Methods: Blood was processed immediately or after 3, 6, 24, and 48 hours, stored at room temperature or 4°C. Cytokines were quantified using a multiplexed Ella assay. Our data showed only IL-2Ra remained stable across all conditions. The remaining cytokine concentrations were significantly impacted by processing delay and storage temperature, with changes evident as early as 3 hours and more pronounced at 24 and 48 hours (p < 0.05). Storing blood at 4°C generally mitigated changes compared to room temperature, but analyte-specific and matrix-dependent variations persisted. These findings emphasize delayed processing significantly alters cytokine levels, highlighting the importance of prompt, standardized processing and careful consideration of pre-analytical factors for reliable cytokine quantitation in clinical studies.