Background: The platelet functionality of cold-stored platelets remains a subject of debate. Our aim was to investigate the effect of temperature on the hemostatic properties of stored platelets. Methods: Ten split pooled platelets stored at cold and at room temperature were evaluated in vitro on storage days 1, 5, 10, and 15 for metabolic, physiological, and vesiculation parameters, as well as their hemostatic profile using rotational thromboelastometry (ROTEM^®). Results: The integrity profile was better preserved in the cold-stored platelets, as lower lactate dehydrogenase levels were documented (e.g., day 10: 261 ± 46 vs. 572 ± 220 U/L, 4 vs. 22 °C, p = 0.004). A time-dependent decrease in hemostatic capacity was evident regardless of the temperature, but the cold-stored units were linked to shorter clot initiation times and increased elasticity, strength, and firmness parameters, especially during extended storage (e.g., maximum clot firmness, INTEM day 15: 81 ± 2 vs. 19 ± 4 mm, 4 vs. 22 °C, p = 0.0008). Additionally, the aggregation of cold-stored platelets was superior after the addition of any agonist tested. Regarding vesiculation parameters, the extracellular vesicles of the units at 4 °C were characterized by a larger size from day 10 onwards, when they also presented higher procoagulant activity (e.g., phospholipid-dependent clotting time of day 15: 21.4 ± 2.3 vs. 25.0 ± 3.0 s, 4 vs. 22 °C, p = 0.016). Conclusion: Our results indicate that cold-stored platelets perform better than those stored at room temperature, demonstrating superior clot formation and stability. This suggests that cold storage may more effectively preserve platelet function, potentially offering advantages for transfusion therapy and the extension of shelf-life. However, the clinical relevance of these findings requires further investigation.

We investigated the antibody kinetics after vaccination against COVID-19 in healthcare workers of a Greek tertiary hospital. Eight hundred and three subjects were included, of whom 758 (94.4%) received the BNT162b2 vaccine (Pfizer-BioNTech), eight (1%) mRNA-1273 (Moderna), 14 (1.7%) ChAdOx1 (Oxford-AstraZeneca) and 23 (2.9%) Ad26.COV2.S (Janssen). Before the second dose, at 2, 6 and 9 months after the second dose and at 2 and 6 months after the third dose, anti-spike IgG were quantified by the chemiluminescence microparticle immunoassay method. One hundred subjects were infected before vaccination (group A), 335 were infected after receiving at least one vaccine dose (group B), while 368 had never been infected (group C). Group A presented a greater number of hospitalizations and reinfections compared to group B (p < 0.05). By multivariate analysis, younger age was associated with an increased risk of reinfection (odds ratio: 0.956, p = 0.004). All subjects showed the highest antibody titers at 2 months after the second and third dose. Group A showed higher antibody titers pre-second dose, which remained elevated 6 months post-second dose compared to groups B and C (p < 0.05). Pre-vaccine infection leads to rapid development of high antibody titer and a slower decline. Vaccination is associated with fewer hospitalizations and fewer reinfections.

The complex interplay between donor and recipient factors likely influences transfusion outcomes in transfusion-dependent thalassemia (TDT). We investigated physiological responses to transfusion shortly after it and 1 week later, focusing on hemoglobin (Hb) increment (ΔHb) and its determinants, using longitudinal data from 36 patients with TDT and 58 red blood cell (RBC) units. Immediate anemia correction after transfusion was associated with decreases in platelets and nucleated RBCs, increases in ADAMTS13 antigen and plasma amino acid levels, and temporary rises in hemolysis and phthalates. One week after transfusion, at the peak of erythroid suppression, plasma antioxidants and mechanical hemolysis decreased, whereas proteasome activity at the RBC membrane increased. Leukocyte levels declined, markers of thrombotic risk and endothelium dysfunction improved, and hepcidin as well as plasma glutamine and deoxyadenosine, increased. In addition to female sex and anemia, ΔHb was influenced by recipient baseline monocyte levels, hypercoagulability, and plasma metabolites, such as methionine, adenosine, acyl-carnitines, and bile acids. Donor RBC unit factors, including residual platelet levels, RBC proteasome activity, arginine metabolism, and catecholamine content also had significant correlations. Notably, the baseline neutrophil-to-lymphocyte ratio strongly affected ΔHb soon after transfusion, after adjusting for confounders. At the 1-week mark, ΔHb correlated with storability markers, such as oxidative hemolysis and phthalates, which, to our knowledge, is a first-ever described connection. Importantly, the percentage of phosphatidylserine-exposing donor RBCs and the uric acid–dependent antioxidant capacity of the RBC units significantly influenced ΔHb at the 1-week time point. These findings enhance our understanding of transfusion dynamics, paving the way for more personalized and effective care strategies in TDT management.

Factor XII (FXII) deficiency is a coagulation factor disorder inherited in an autosomal recessive manner that causes prolonged activated partial thromboplastin time (aPTT). Although it is clinically benign without additional bleeding risk, it has been associated with paradoxical thrombosis. We report the case of a 38-year-old woman who presented with cardiac arrest secondary to spontaneous coronary artery dissection (SCAD) in the absence of identifiable risk factors. Laboratory investigations revealed an isolated prolonged aPTT, which was corrected with mixing studies, and a severe FXII deficiency with activity levels < 1%. Molecular analysis identified two homozygous FXII gene variants: the 46C>T polymorphism and the c.619G>C (p.Ala207Pro) variant. The two variants are considered clinically benign, although the combination of both in a single individual has not been previously reported. The coexistence of FXII deficiency in this case may be of clinical and hypothesis-generating interest.