Hemolytic transfusion reactions seldom occur because the incidence of unexpected antibodies in random patients is relatively low, e.g., 3-5% is sometimes cited.

Being transfused with O Rh negative RBC is irrelvant if you have an unexpected antibody like anti-K or anti-c.

Incompatible red cells may "bleed out" but only if bleeding is brisk. Even then, a hemolytic reaction may occur later once the patient's antibody rebounds and destroys remaining antigen-positive donor red cells.

It's true that some patients have only cold-reactive antibodies that will not react at body temperature. But this does not explain why warm-reactive red cell antibodies cause few reactions

Why do so few patients transfused with un-crossmatched red cells in an emergency experience a hemolytic transfusion reaction? Select the one best reason.