Patients with AIHA and warm RBC autoantibodies do not have the spontaneous agglutination of RBCs but can still have significant hemolysis as the RBCs coated with autoantibodies are removed by the reticuloendothelial system, which also presents with signs and symptoms of anemia and hemolysis.
Cold RBC autoantibodies can cause spontaneous agglutination, observed as clumping of the RBCs on the test (Figure, B).