Cold autoantibodies can interfere with routine blood bank tests. The extent to which they interfere depends on the concentration and thermal amplitude of the antibody. A blood bank technologist must recognize these problems and work through the resolution of cold autoantibody cases.
Red blood cells that are heavily coated with cold antibody may cause false positive reactions during ABO typing, resulting in an ABO discrepancy. To determine if a cold autoantibody is involved, Group O and autologous red blood cells can be tested with the patient's plasma. Both will likely be positive if a cold autoantibody is present. Two methods can be used to resolve this type of discrepancy:
- The patient's sample can be prewarmed to 37°C prior to testing.
- Patient red blood cells can be washed with saline warmed to 37°C.
The warm incubation promotes dissociation of the antibody from the red cell and the warm washes prevent it from reattaching in vitro.
Cold autoantibodies can also cause false-positive reactions during Rh (D) typing. In addition to the methods listed above, using monoclonal low-protein reagents may also minimize false positive Rh(D) typing reactions due to cold autoantibodies. If polyspecific antihuman globulin reagents are used during weak-D testing, false positive reactions can occur due to complement activation of cold IgM autoantibodies. This can be prevented by using monospecific anti-IgG or using samples collected in EDTA.