Infants may have active hemolysis caused by ABO incompatibility and have a negative DAT; however, in such infants, the peripheral blood smear should reveal microspherocytes, and the indirect antiglobulin (indirect Coombs) test is usually positive because it identifies plasma ABO antibodies, which, in the presence of adult RBCs (adult RBCs have well discriminated ABO antigens), give a positive test result.