In the blood, red blood cells are normally detached from one another. When red blood cells are agglutinated (clumped) together, they are destroyed more quickly, which can lead to hemolytic anemia. The agglutination of red blood cells can be caused by a breakdown in the immune system when it begins to produce antibodies against the surface of its own red blood cells. When this agglutination is chronic and tends to occur at temperatures colder than room temperature, it is called “cold agglutinin disease” or CAD. The test is usually prescribed for individuals with anemias accompanied by painful blue discolouration of extremities (fingers, toes, ears, nose) exposed to the cold. Certain other conditions (mycoplasma pneumonia, infectious mononucleosis, certain cancers and infections) may also cause cold agglutinins.
Cold agglutinin test results are expressed as either negative or positive. If positive, a dilution titer is given. A titer below 64 (visible agglutination on plasma that has been diluted 64 times or less) can sometimes be observed in normal individuals. The higher the dilution titer, the higher the concentration of antibodies responsible for agglutination and the more severe the symptoms.