Cold agglutinins

Cold-agglutinins:Antibodies that cause agglutination of red blood cells (RBCs) at low temperature, otherwise known as cold agglutinins, are common. Low titers are frequently identified in healthy individuals and are clinically insignificant. Elevated titers (>1:32) are associated with several disease states, such as Mycoplasma pneumoniae infection or lymphoproliferative disorders. Cold agglutinins often have blood group specificity for the I-i system and usually belong to the IgM class of antibodies. As such, they typically cannot cross the placental membrane and are not likely to be a significant risk for hemolytic disease of the fetus and newborn (HDFN). Rarely, the thermal range of cold agglutinins can extend up to body temperature and result in agglutination and lysis of RBCs, such as in Raynaud phenomenon and hemoglobinuria in cold weather (cold agglutinin syndrome). Cold agglutinins have also been reported to cause cardiac ischemia during procedures that use cold cardioplegia. Keeping the patient warm and warming of the blood prior to transfusion may help to prevent agglutination and lysis of RBCs.