Useful in supporting the diagnosis of primary atypical pneumonia, infection with Mycoplasma pneumoniae, and hemolytic anemia, gangrene, cirrhosis, Raynaud’s disease, some viral diseases, and infectious diseases such as staphylococcemia, influenza, and tuberculosis. Cold agglutinins can cause intravascular agglutination (acrocyanosis) or hemolysis (due to the fixing of complement) in the peripheral circulation, causing pain and discoloration of extremities upon exposure to cold. Primary (chronic) cold agglutinin syndrome (CAS) is typically due to the presence of kappa light chain monoclonal autoantibodies to erythrocytic polysaccharide antigens (e.g., I, i and Pr) related to the ABO and Lewis blood groups.