Which of the following results indicates that the source of a positive reaction in the autocontrol should be investigated further?

In the context of blood banking, the autocontrol is a crucial test used to determine whether a patient's serum reacts with their own red blood cells, which can indicate the presence of an autoantibody or a positive reaction due to other factors, such as recent transfusions or underlying medical conditions.

A positive reaction in the autocontrol with one of the screening cells suggests that there may be an autoantibody or some other condition affecting the patient's blood. In this case, when Screening cell I shows a negative reaction (0) and Screening cell II shows a positive reaction (3+), it indicates that the positive autocontrol reaction is not due to the patient's own red blood cells, as those cells did not react. However, the significant positive reaction with Screening cell II suggests that something else—potentially an antibody present in the patient's serum causing the reactivity—needs further investigation.

This scenario highlights the importance of observing the reactions of both screening cells to assess the source of the positive result. When encountering a scenario where one screening cell reacts strongly while the other does not, it's a clear indicator that further testing, such as a panel study or additional serologic testing, might be required to identify the specific antibody involved and determine the appropriate management for the patient.