A recently transfused patient shows anti-A 2+ in forward typing and B 3+ in reverse typing. What is the probable cause?

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Multiple Choice

A recently transfused patient shows anti-A 2+ in forward typing and B 3+ in reverse typing. What is the probable cause?

The pattern reflects a typing discrepancy caused by a mixed population of red cells from donor and recipient after transfusion. Forward typing tests the patient’s red cells with anti-A; a positive reaction indicates A antigen is present on circulating cells. Reverse typing tests the patient’s serum with B cells; a positive reaction there shows anti-B antibodies in the plasma, which is typical of a person with type A blood. If the patient has recently received blood, some donor cells may still be circulating. To produce A antigen on some cells but not others (a mixed field), the donor population would need to include A-bearing cells and non–A cells, which is achieved by mixing A and O blood. Transfusion with AB or B blood would introduce B antigen-bearing cells too, and would create a different forward-typing pattern than what’s described. Therefore, the most likely cause is transfusion of A and O blood, resulting in a mixed red cell population that yields this typing pattern.

The pattern reflects a typing discrepancy caused by a mixed population of red cells from donor and recipient after transfusion. Forward typing tests the patient’s red cells with anti-A; a positive reaction indicates A antigen is present on circulating cells. Reverse typing tests the patient’s serum with B cells; a positive reaction there shows anti-B antibodies in the plasma, which is typical of a person with type A blood.

If the patient has recently received blood, some donor cells may still be circulating. To produce A antigen on some cells but not others (a mixed field), the donor population would need to include A-bearing cells and non–A cells, which is achieved by mixing A and O blood. Transfusion with AB or B blood would introduce B antigen-bearing cells too, and would create a different forward-typing pattern than what’s described. Therefore, the most likely cause is transfusion of A and O blood, resulting in a mixed red cell population that yields this typing pattern.

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