Background: Like other viruses, the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) appears to be responsible for several autoimmune complications. The occurrence of autoimmune hemolytic anemia has been described in several case reports. This AIHA was also noticeable by the important number of blood transfusions required for COVID-19 (coronavirus disease 2019) patients. By investigating RBC coating autoantibodies, this article attempts to clarify the autoimmune aspect of the anemia in the context of SARS-CoV-2 infection. Results: A large population of COVID-19 patients selected at Saint-Luc University Hospital showed an average of 44% DAT positivity. In this population, the intensive care patients were more prone to DAT positivity than the general ward patients (statistically significant result). The positive DAT appeared « transmissible » to other RBCs via COVID-19 DAT-positive patient’s plasma. Conclusion: The strongest hypothesis explaining this observation is the targeting of cryptic antigens by autoantibodies in COVID-19 patients.

Introduction Lupus anticoagulant (LA) testing requires normal pooled plasma (NPP) in performing mixing studies and can be used for normalized ratios of clotting times (CTs). The aims were to demonstrate whether significant differences in clotting times between two batches of a same commercial NPP (CRYOcheck™) directly affect NPP‐based cut‐off values. Methods Diluted Russell Viper venom time (DRVVT) and activated partial thromboplastin time (aPTT) were used for LA testing. Screening, mixing and confirm tests were performed with Stago® instruments and reagents. Two batches of commercial NPP (A1291 and A1301 from CRYOcheck™; frozen) were compared in the determination of cut‐off values. Cut‐off values were defined as 99th percentile values of 60 healthy donors and compared with Mann–Whitney U test. Results Cut‐off values obtained with the two NPP batches were significantly different for DRVVT (screen normalized ratio: 1.09 vs. 1.24, screen mix: 41.9 s vs. 38.9 s; index of circulating anticoagulant: 5.0 vs. 8.4; all had p‐value <.001). On the contrary, no significant differences were observed for aPTT (screen normalized ratio: 1.32 vs. 1.34; p‐value = .4068, screen mix: 37.8 s vs. 38.1 s; p‐value = .1153) except for index of circulating anticoagulant: 9.6 versus 10.4 (p‐value <.05). Conclusion This study demonstrates that differences between two commercial NPP batches produced by a same manufacturer influenced LA cut‐off values used for mixing studies and normalized ratios. Adequate cut‐off setting, taking into account NPP CTs, is important to provide accurate conclusion about the presence or absence of a LA and avoid potential clinical impact.

In this unprecedented crisis of severe acute respiratory syndrome coronavirus 2 and its associated coronavirus disease 2019 (COVID-19), polymerase chain reaction and then serological testing platforms have been massively developed to face the important screening demand. Polymerase chain reaction and serological testing platforms are not the only actors impacted by the crisis, transfusion services are facing important difficulties. A positive direct antiglobulin test is frequently observed for patients encountering COVID-19. Patients with severe symptoms may develop anaemia and become good candidates for blood transfusions. The interpretation of a positive direct antiglobulin test for patients recently transfused and suffering from COVID-19 is complex. The differentiation between COVID-19 induced antibodies and possible associated transfusion alloantibodies is therefore crucial. In this context, the elution technique incorporated in an appropriate decision-making process plays its full role. This intricate topic is presented through a case report followed by literature review and finally decision-making process for COVID-19 patients necessitating red blood cells administration.

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Introduction Studies about the duration of the humoral and cellular response following the bivalent booster administration are still scarce. We aimed at assessing the humoral and cellular response in a cohort of healthcare workers that received this booster. Material and methods Blood samples were collected before the administration of the bivalent booster from Pfizer-BioNTech and after 14, 28, 90, and 180 days. Neutralizing antibodies against either the D614G strain, the delta variant, the BA.5 variant, or the XBB.1.5 subvariant were measured. The cellular response was assessed by measurement of the release of interferon gamma (IFNγ) from T cells in response to an in vitro SARS-CoV-2 stimulation. Results A substantial waning of neutralizing antibodies was observed after 6 months (23.1‐fold decrease), especially considering the XBB.1.5 subvariant. The estimated T of neutralizing antibodies was 16.1 days (95% CI=10.2–38.4 days). Although most participants still present a robust cellular response after 6 months (i.e., 95%), a significant decrease was also observed compared to the peak response (0.41 versus 0.95 UI/L, p=0.0083). Conclusion A significant waning of the humoral and cellular response was observed after 6 months. These data can also help national competent authorities in their recommendation regarding the administration of an additional booster.