2018 Volume 67 Issue 2 Pages 184-188
We usually prepare products of the same blood type for transfusion; however, in emergency cases, we prepare unmatched type O red blood cells. The necessity of emergency transfusions has been increasing recently. It is often difficult to identify the patient’s original blood type after the transfusion of type O red blood cells because the original patient’s blood and the transfused blood are mixed and mixed-field agglutination (mf) can be found. In the determination of the blood type of such patients, the transfused blood is found at the bottom after sample centrifugation because mature erythrocytes show increased weight with time. The sampling position may affect the judgement of “mf”. In this study, we investigated four causes that affect the typing of the blood, namely, the mixed type O cell concentration, the staff members’ ability, the differences in the reactivity of erythrocytes over time, and the reproducibilities of two different automated analyzers and the slide method. We found that a mixture of more than 2 units (about 10% of the circulating blood) of type O red blood cells can be examined even when the “mf” was found in any of these methods. Mixed-field agglutination might not be detected by the slide method when an inexperienced staff member examines or when mature erythrocytes were transfused. The samples with 10% type O red blood cells were judged as “mf” in 11 out of 15 tests, because the automated analyzer usually aspirates samples from the bottom. The sampling position is critical for the decision of the blood type when testing samples of mixed cells with different specific weights. When an unexpected reaction occurs, we should check the patient’s clinical background and try to test by another appropriate method.
