How do you test for cold antibodies?
The cold agglutinin test measures the levels of cold agglutinins in a patient’s blood. The clinician takes a blood sample from the patient and separates it into several vials. Each portion of the sample is then diluted to a different level, and cooled overnight to determine at what dilution the patient’s blood clots.
What tests are used to diagnose cold agglutinin?
Blood studies used in the diagnosis of cold agglutinin disease include the following:
- Complete blood cell count (CBC) with differential.
- Peripheral blood smear.
- Reticulocyte count.
- Direct Coombs test (direct antiglobulin test [DAT])
- Serum protein electrophoresis and serum immunoelectrophoresis (immunofixation)
What is a cold autoantibody and how is it identified?
Any red cell antibody that binds its target antigen best at levels below body temperature (37 C) is commonly referred to as a “cold antibody” (this, of course, contrasts to “warm” antibodies that react best at or near body temperature).
What is direct Coombs test?
The direct Coombs test is used to detect antibodies that are stuck to the surface of red blood cells. Many diseases and drugs can cause this to happen. These antibodies sometimes destroy red blood cells and cause anemia.
How is cold autoimmune hemolytic anemia diagnosed?
Autoimmune hemolytic anemia is diagnosed by detection of autoantibodies with the direct antiglobulin (direct Coombs) test. Antiglobulin serum is added to washed RBCs from the patient; agglutination indicates the presence of immunoglobulin or complement (C) bound to the RBCs.
When are cold antibodies clinically significant?
Generally, a titer ≥64 is considered clinically significant. (See ‘Antibody titer and thermal amplitude’ below.) Thermal amplitude – As noted above, cold agglutinins react with RBCs at colder temperatures than normal core body temperature.