Thermal amplitude is a test used to determine the highest temperature the antibody will bind to the antigen. This, along with cold agglutinin titer, helps to determine the clinical significance of the cold autoantibody. Thermal amplitude can be used as a guide for surgical procedures that bring the body temperature down to determine how far down they can bring the patient's temperature before the cold agglutinin starts reacting. This is commonly done in cardiac procedures.
Antibody screens using the patient's plasma and donor RBCs are performed at 4oC, 22oC, 30oC, and 37oC for 1 hour and observed for agglutination.
A Thermal amplitude >30oC is considered clinically significant and associated with potential accelerated RBC destruction. Normal patients will often have agglutination seen at 4oC. However, in patients with CAD, the agglutination continues through to 30oC or higher.
