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Finding the right type
Blood type matching is important for pregnancy, blood transfusion, and bone marrow transplantation. Zhang et al. developed a blood typing assay based on the color change that occurs when a common pH indicator dye reacts with blood. Red blood cells (RBCs) and plasma were separated from small volumes of whole, uncentrifuged blood samples using antibodies immobilized on paper test strips. The assays performed forward grouping (detecting A and/or B antigens on RBCs) and reverse grouping (monitoring the agglutination between RBCs and anti-A and/or anti-B antibodies in plasma) within 2 min and could also perform Rhesus and rare blood typing. A machine-learning algorithm grouped human blood samples automatically on the basis of spectral analysis of the colorimetric assay readouts. This economical and robust assay is useful for time- and resource-limited environments.
Fast and simultaneous forward and reverse blood grouping has long remained elusive. Forward blood grouping detects antigens on red blood cells, whereas reverse grouping identifies specific antibodies present in plasma. We developed a paper-based assay using immobilized antibodies and bromocresol green dye for rapid and reliable blood grouping, where dye-assisted color changes corresponding to distinct blood components provide a visual readout. ABO antigens and five major Rhesus antigens could be detected within 30 s, and simultaneous forward and reverse ABO blood grouping using small volumes (100 μl) of whole blood was achieved within 2 min through on-chip plasma separation without centrifugation. A machine-learning method was developed to classify the spectral plots corresponding to dye-based color changes, which enabled reproducible automatic grouping. Using optimized operating parameters, the dye-assisted paper assay exhibited comparable accuracy and reproducibility to the classical gel-card assays in grouping 3550 human blood samples. When translated to the assembly line and low-cost manufacturing, the proposed approach may be developed into a cost-effective and robust universal blood-grouping platform.
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