Person A is in an accident and needs blood. Person A happens to have A+ blood. Which of the following types of blood can be given to Person A without killing him? *
1 point
1. A+, A-, B+, B-
2. A+, O+, AB+, A-
3. A+, O+, AB-, O-
4. A+, O+, A-, O-

4. A+, 0+, A-, 0-

Explanation: Incompatibility between blood types works as follows:

Rh-negative (-) patients are incompatible to receive Rh-positive (+) blood. The inverse is NOT true; a Rh+ patient may receive Rh- blood without ill effects.

Patients with blood type A are compatible with either A or 0 blood types. Exposure to the B antigen, present in type B or AB blood, may cause an adverse reaction.

Conversely, patients with blood type B are compatible with either B or 0 blood types. Again, an adverse reaction may take place in case of exposure to the A antigen present in type A or AB blood.

Finally, patients with blood type 0 may react adversely to both A and B antigens. Therefore, they may only receive type 0 blood.

Regarding the initial statement: Note that the immune reaction caused by a transfusion mismatch, while definitely a medical emergency, may not necessarily lead to the death of the patient if handled appropriately.