Cold Agglutinin Disease (CAD)

Autoimmune hemolytic anemia (AIHA) is classified into warm and cold reactive antibody types.1 Cold hemagglutination was first described in 1903.2 Later, in 1937, Rosenthal and Corten provided a description of the association between cold hemagglutination and hemolysis. Systematic descriptions of 16 patients with cold agglutinin disease (CAD) were published during the 1960s by Dacie and Schubothe.1 Cold agglutinins (CAs) are measured in a semiquantitative manner, with the titer determined according to their ability to cause red blood cell agglutination at 4oC.2 In the conventional classification, CAD comprises 2 types: primary or idiopathic CAD, which is not related to any underlying disease, and secondary CAD, which occurs in association with malignant disease, mainly lymphomas or other cancers, or with acute infections1,2 and autoimmune disorders such as systemic lupus erythematosus and rheumatoid arthritis.3 

Primary Cold Agglutinin Disease

Primary cold agglutinin disease is usually characterized by monoclonal cold-reacting autoantibodies. The disease is chronic and generally develops after the age of 50 years. The peak incidence is noted in the seventh and eighth decades.4 Primary CAD accounts for 15% of all cases of AIHA.Primary CAD is described as a form of AIHA that is mediated by CAs in the absence of any underlying disease, such as an aggressive lymphoma, another overt malignancy, or a specific infection. CAs are autoantibodies that cause erythrocytes to agglutinate at an optimal temperature of 3°C to 4°C, but they may also react at higher temperatures, depending on the thermal amplitude. CAD has recently been labeled a distinct clinicopathologic entity. It is not a syndrome, but a disease.6

Cold Agglutinin Disease Types
Microscopic view of cold agglutinin disease (CAD), autoimmune hemolytic anemia
Credit: Getty Images

All patients with CAD show evidence of hemolysis, but sometimes they do not have anemia because the hemolysis is completely compensated.4 The circulatory symptoms may be slight or disabling.2 The characteristic feature of CAD, seen in more than 90% of patients, is the presence of cold-induced circulatory symptoms.The symptoms vary from moderate acrocyanosis to severe Raynaud phenomenon that is brought on even by mild exposure to cold. In cooler areas, typical seasonal variations in the severity of hemolytic anemia have been reported.1,2,5 

The diagnostic criteria for primary CAD include evidence of hemolysis, a cold agglutinin titer above 1:64 at 4oC, characteristic direct antiglobulin test (DAT) findings (eg, polyspecific DAT positivity and specific DAT positivity for C3d, absence of malignant disease on clinical and radiological evaluation).1 

In at least 66% of cases of CAD, febrile infection or major trauma is the precipitating factor in an exacerbation of hemolytic anemia. CAs in primary CAD are often monoclonal immunoglobulin M antibodies, usually with κ light chain restriction. B-cell clonality can be estimated with flow cytometry and/or immunohistochemistry.5

Secondary Cold Agglutinin Disease

Secondary cold agglutinin disease can be associated with either monoclonal or polyclonal cold-reacting autoantibodies. Secondary disease is caused by an underlying lymphoproliferative disorder or infection. The monoclonal form of secondary CAD occurs in adults and is chronic. Polyclonal secondary CAD occurs in children and young adults and is transient in nature.4 

In addition to autoimmune hemolysis, the pathological and clinical characteristics of secondary CAS depend on the underlying disease. Cold-antibody AIHA due to underlying infection commonly occurs in adolescents or young adults with infectious mononucleosis caused by Epstein-Barr virus or in individuals with Mycoplasma pneumoniae pneumonia. In such cases, the findings of anemia and hemoglobinuria suggest the possibility of secondary AIHA. In addition to the tests used to diagnose infection, a hemolysis workup, polyspecific and monospecific DATs, and titration of cold agglutinins help to confirm the diagnosis. In a few patients, paroxysmal cold hemoglobinuria and exacerbation of primary CAD by infection must be excluded before secondary CAS is diagnosed.5

In general, the proper handling of specimens is crucial during testing for cold agglutinins. In ordinary circumstances, blood samples are kept in a laboratory refrigerator until testing is done, but in the case of cold agglutinins, this practice has to be avoided.The blood must be kept warm until it is tested. The blood studies conducted to diagnose CAD include a complete blood cell count (CBC), peripheral blood smear, reticulocyte count, DAT, serum protein electrophoresis, serum immunoelectrophoresis or immunofixation, and cold agglutinin titer.7 


  1. Berentsen S, Beiske K, Tjønnfjord GE. Primary chronic cold agglutinin disease: an update on pathogenesis, clinical features and therapy. Hematology. 2007;12(5):361-370. doi:10.1080/10245330701445392 
  2. Berentsen S, Randen U, Tjønnfjord GE. Cold agglutinin-mediated autoimmune hemolytic anemia. Hematol Oncol Clin North Am. 2015;29(3):455-471. doi:10.1016/j.hoc.2015.01.002
  3. Brugnara C, Berentsen S. Cold agglutinin disease. Last updated on Apr 22, 2021, Assessed on Sep 2, 2021.
  4. Aljubran SA. Cold agglutinin disease. Medscape. Updated August 23, 2021, Accessed September 3, 2021.
  5. Berentsen S, Tjønnfjord GE. Diagnosis and treatment of cold agglutinin mediated autoimmune hemolytic anemia. Blood Rev. 2012;26(3):107-115. doi:10.1016/j.blre.2012.01.002
  6. Berentsen S. Cold agglutinin disease. Hematology Am Soc Hematol Educ Program. 2016;2016(1):226-231. doi:10.1182/asheducation-2016.1.226
  7. Aljubran SA. Cold agglutinin disease workup. Updated August 23,  2021. Accessed September 3, 2021.

Reviewed by Kyle Habet, MD, on 9/7/2021.