High-throughput and rapid serology assays to detect the antibody response specific to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) in human blood samples are urgently required to improve our understanding of the effects of COVID-19 across the world. Short-term applications include rapid case identification and contact tracing to limit viral spread, while population screening to determine the extent of viral infection across communities is a longer-term need. Assays developed to address these needs should match the ASSURED criteria. We have identified agglutination tests based on the commonly employed blood typing methods as a viable option. These blood typing tests are employed in hospitals worldwide, are high-throughput, fast (10–30 min), and automated in most cases. Herein, we describe the application of agglutination assays to SARS-CoV-2 serology testing by combining column agglutination testing with peptide–antibody bioconjugates, which facilitate red cell cross-linking only in the presence of plasma containing antibodies against SARS-CoV-2. This simple, rapid, and easily scalable approach has immediate application in SARS-CoV-2 serological testing and is a useful platform for assay development beyond the COVID-19 pandemic.

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Prior to transfusion of red blood cells (RBCs), recipients must be tested for the presence of alloantibodies to avoid immune complications. Liquid‐preserved reagent RBCs with known blood group antigen phenotypes are used for testing. However, these reagents have practical constraints, including limited shelf‐life and require constant refrigeration. To address these issues, we explore the effects of rapid freeze‐drying conditions with trehalose cryoprotectant (0.1–1 M concentrations) on human RBCs and storage of freeze‐dried RBCs (FDRBCs) at room temperature (RT) for up to 12 months. We report that rapid freeze‐drying of RBCs for 2.5 hr with 0.5 M trehalose achieves recoverable cells with near‐normal morphological shape, although size‐reduced. The FDRBCs are metabolically active and functional in antibody‐agglutination tests by the column agglutination test (CAT) for ABO and Rhesus‐D blood group antigens. Expression of the Duffy blood group protein (CD234) decreases by 50% after freeze‐drying RBCs. The initial recovery rate is ≤25%; however, 43% of these FDRBCs are still recoverable after RT storage for 12 months. In this proof‐of‐principle study, we show that rapid freeze‐drying can stabilize RBCs. Further refinements to improve the recovery rate and preservation of antigenic epitopes will make FDRBCs a practical alternative source of reagent RBCs for pre‐transfusion alloantibody identification.

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Oxidative treatment of human red blood cells (RBCs) prior to freeze-drying appears to stabilize the RBCs to withstand dried storage at room temperature. To better understand the effects of oxidation...