In vitro haemostatic functionality of INTERCEPT (Amotosalen, UVA) pathogen-reduced platelet concentrates is not affected by cold-storage

Introduction Platelet concentrates (PCs) are used to prevent or treat bleeding. PCs are stored at room temperature (RT) for a maximum of 4 days (Germany) due to the risk of bacterial growth which might cause transfusion-transmitted bacterial infection (TTBI). To prevent this, pathogen-inactivation (PI) can be applied also leading to a prolonged storage time (5 days in Germany and 7 days in Swiss). Moreover, cold storage (CS) has been investigated as alternative storage condition showing improved cell functionality and extended shelf-life. Also, here PI can be applied to diminish the risk of TTBI. The aim of this study was to examine the potential impact of the combination of CS and PI on the in vitro haemostatic functions of PCs. Method 16 PCs were collected from healthy donors and each one was split in 2 bags. From those, one bag underwent PI (Amotosalen/UVA) while the second one remained untreated (CTR). Both were split in 2 additional bags to get: 2 untreated products one stored at 4°C (4°C-CTR) and the other one at RT (RT-CTR). The same storage conditions were applied to the PI-treated bags (4°C-PI and RT-PI). The expression of CD62P and CD63 (TRAP) was investigated by flow cytometry. Platelet aggregation was assessed by aggregometry assays and thrombin generation using a thrombogram. The clot formation ability was evaluated by thromboelastography (TEG). All analyses were performed after 1, 4, 7 and 10 days of storage. Results The cell counts and pH values matched the physiological ranges in all PCs during the entire storage period. Flow cytometry analyses indicated that CD62P and CD63 expression decreased in a time-dependent manner, to similar levels for RT-PI and 4°C-PI, when compared on the same day. Also, similar aggregation ability was observed between 4°C-PI and RT-PI products after Ristocetin stimulation. While, upon TRAP incubation, a gradual reduction over storage time, with better retention of aggregation for RT-PI samples than 4°C-PI, was detected on day 4 and 7 (p=0.035; p=0.021, respectively). The investigation of the kinetic of thrombin generation showed comparable results, between RT-PI and 4°C-PI samples, for all parameters (Lagtime, time to peak, max. thrombin generation and endogenous thrombin potential) with a similar progressive decrease over time in all products. Finally, a significant increase of clot formation time was measured by TEG, after 7 and 10 days, in 4°C-PI samples compared RT-PI (p=0.039; p=0.044, respectively). Nevertheless, similar maximum clot firmness was detected between RT-PI and 4°C-PI products, during the entire storage period, indicating comparable clot´s stability even if 4°C-PI samples showed enhanced clot formation time. Conclusion Our data suggest that PI-PCs stored at 4°C maintained similar in vitro haemostatic functions compared to RT-PI samples. Therefore, the combination of CS and PI might be a promising strategy to extend the half-life of PCs and reduce the risk of TTBI without impairing cell functions. Publication History Article published online: 17 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany