While RBC agglutination produces clinical signs of hemolytic anemia, cold agglutinin agglutination is a known pre-analytical and analytical component that results in erroneous automated complete blood count (CBC) results. Cold agglutinins are antibodies that recognize antigens on RBCs at low temperatures. As the temperature rises during testing, the antigen becomes exposed, triggering more antibody binding. The result is formation of large aggregates of red blood cells (RBCs), which can be detected by light microscopy. Cold agglutinins may be acute or chronic. Acute cold agglutinins are usually present for less than six months before resolving on their own. Chronic cold agglutinins remain detectable for longer than six months. They can cause significant laboratory abnormalities including anemia, leukopenia, thrombocytopenia, and positive Coombs' test. Patients with chronic cold agglutinins are at risk for developing serious complications such as renal failure, neurological problems, and bone marrow suppression. The only cure for cold agglutinins is removal of the causative agent (i.e., underlying disease). No treatment is available for cold agglutinins themselves. The sensitivity of the CBC varies depending on the specific parameter being measured.