Some important aspects of cold antibodies are:
- Most are IgM and are not clinically significant.
- May interfere with the detection of clinically significant antibodies if they react at the AHG phase.
- Screen cells and panel cells will have positive reactions in the IS phase and strength will diminish or antibody will not be detected at the AHG phase.
- Autocontrol will be positive if the cold antibody is an autoantibody.
The binding of antibody to antigen occurs at room or colder temperatures and may start to disassociate from the red cell membrane at warmer temperatures. Reactions will appear weaker or negative at warmer temperatures (e.g., 4+ at IS phase and W (weak)+ at AHG phase).
Prewarming
If a nonspecific cold antibody or cold agglutinin is suspected, warm the sample and testing reagents, including saline, to 37°C. Only do reaction readings at AHG; bypassing the optimum reaction temperature prevents activation and binding of the cold antibody.
