Background/Objectives: Leukoreduced low-titer group O whole blood (LTOWB) is a promising option for early transfusion in massive hemorrhages, by providing red blood cells (RBCs), plasma, and platelets in a single unit. This study aimed to assess the effects of pathogen reduction (PR) on the LTOWB quality and its suitability for emergency transfusions, including its post-thaw RBC usability. Methods: Whole blood from 24 donors was processed and analyzed over seven days, including post-thaw assessments. Hematological and coagulation parameters, along with atomic force microscopy, were used to assess the RBCs’ morphology, cytoskeletal integrity, and nanomechanical properties. Results: The PR reduced the leukocyte content while preserving platelet counts at the level of the control group. Although certain clotting factors, such as fibrinogen (p < 0.001) and factor VIII (p < 0.001), were diminished after the PR, thromboelastometry results remained within reference ranges, indicating a maintained hemostatic potential. Morphological changes in RBCs were observed, but the membrane elasticity remained stable throughout storage and after thawing, indicating preserved macromechanical properties essential for hemostasis. Conclusions: These findings demonstrate that LTOWB treated with partial a leukoreduction and PR maintains functional and structural integrity, supporting its potential utility as a safe and effective transfusion product for managing acute blood loss.

INTRODUCTION: Currently, whole (preserved) blood is a promising tool for transfusion therapy in cases of massive blood loss. However, the lack of universal technological solutions that minimize immunological and infectious risks of preserved blood limits its widespread use. OBJECTIVE: To study the impact of modified collection methods and pathogen reduction technology on the properties of preserved blood that determine its suitability for the correction of massive blood loss. MATERIALS AND METHODS: Whole blood of group O was collected from 44 donors (34 men and 10 women). Four groups were studied: the control group without leukoreduction (Control), leukoreduced (LR), collected using a modified technology with partial leukoreduction (PLR), and with subsequent pathogen reduction (PLR + PR). Blood samples were stored at +4–6 °C for 7 days. On days 1 and 7 hematological parameters, coagulation factors, and viscoelastic tests were evaluated. Atomic force microscopy (AFM) was used to assess erythrocyte morphology, cytoskeletal structure, and cell elasticity modulus. RESULTS: Partial leukoreduction reduced leukocyte counts to 0.36 × 109/L, with similar levels observed in PLR + PR and no significant changes during storage. Platelet levels remained stable in both groups: 139 (102; 164) × 109/L and 86 (43; 107) × 109/L in PLR, and 114 (94; 142) × 109/L and 70 (55; 96) × 109/L in PLR + PR on days 1 and 7, respectively. Coagulation properties (NATEM test) remained within reference ranges; fibrinogen levels were lower in the pathogen-reduced group, while Factor XIII remained stable throughout storage. AFM analysis showed that erythrocyte morphological changes after pathogen reduction did not exceed those observed in other groups; no negative effects on cytoskeletal structure or cell elasticity were detected. The Young’s modulus remained at 5.5 ± 2 kPa across all groups. CONCLUSIONS: Modified blood collection technologies preserve the hemostatic potential of preserved blood and do not significantly affect the structure of erythrocytes. Partial leukoreduction and pathogen reduction could become universal technological solutions that enhance the safety of using preserved blood for correcting massive blood loss.