Standard Operating Procedures in Biorepositories and Biobanks.

Whole blood represents one of the most practical and frequently collected human biospecimens. Its accessibility and minimally invasive collection make it a cornerstone for both clinical studies and laboratory research. Once obtained, whole blood can be fractionated into multiple components that provide valuable material for diverse experimental purposes. Plasma, serum, and peripheral blood mononuclear cells (PBMCs) are among the most widely used derivatives, each offering distinct analytical advantages, from biomarker discovery to immunological profiling. Data reproducibility and clinical translation depend heavily on biospecimen quality; maintaining the integrity of whole blood samples throughout processing, storage, and handling is of paramount importance. Variability introduced during these steps can compromise cell viability, distort biomarker profiles, and reduce confidence in study outcomes. Standardized operating procedures (SOPs) serve as a critical safeguard by minimizing inconsistencies, ensuring regulatory compliance, and reinforcing trust in biobanking practices. This chapter details four well-validated SOPs for processing whole blood collected in blood collection tubes (BCT). These SOPs describe methods for preparing Double-Spun Plasma and Serum, and for isolating PBMCs using two complementary approaches, with particular emphasis on strategies that preserve sample quality and integrity across all stages of processing.