While the mistake with the blood was not really a problem, the American military did not test for RH factor during the Korean conflict as dog tags were only marked 'A, B, AB, or O' but did not show the RH factor until sometime after the Korean War.
An early sign of Captain Whitfield's drinking problem is her bringing AB-Negative blood instead of the requested AB-Positive in the operating room and being called out by Klinger for nearly making a mistake. Yet a person with blood type AB-Positive can accept AB-Negative blood without consequence. AB-Positive blood is known as the "universal recipient" because it can be transfused with any other type.