Answer: a. use of refrigerated clotted blood samples in which complement components coat RBCs in vitro
Step-by-step explanation:
DAT is direct antiglobulin test. It is also called as Coombs test. It is primarily used for determining the cause of hemolytic anemia. This test looks for the attachment of the antibodies that break apart the red blood cells causing hemolysis.
A false positive DAT result signifies that the eluted antibody cannot bind to the red blood cells. But binding do occur in true positive test.
Thus the result may reflect that it has been conducted on the refrigerated and clotted blood samples yielding a false result in inappropriate results.