Resolving Incompatible Blood Cross-Matching: The Role of 37°C Water Bath in Transfusion Safety.

Background: Incompatible cross-matching at room temperature can delay critical blood transfusions. We report that red cells from patients requiring blood transfusion agglutinated after cross-matching at room temperature, but changed from agglutination to dispersion after a water bath at 37°C. The aim was to investigate whether re-cross-matching at 37°C is necessary for some patients with incompatible cross-matching. Methods: This prospective observational study analysed all incompatible cross-matched blood samples at the Blood Transfusion Department of Chifeng Municipal Hospital from 1 May 2024 to 31 July 2024. Cross-matching was performed using a fully automated system and the Polybrene method. For incompatible samples, the Polybrene method was repeated after the samples were placed in a 37°C water bath for 5 minutes. Results: Thirty patients with cross-match incompatibilities were included. Among these, agglutination was reversed after the 37°C water bath in 28 patients, indicating compatibility. Only 2 patients had true blood group incompatibility. We detail the results of one representative patient from the 28 with reversed agglutination. This patient showed agglutination using the fully automated device and the Polybrene method, but not with the saline method. After a 37°C water bath, the agglutinated erythrocytes dispersed into a single-cell state upon microscopic examination. Conclusion: For selected patients, cross-matching at 37°C can resolve false-positive agglutination, ensuring transfusion safety and timely access to blood products. This simple method can be integrated into the clinical cross-matching workflow.