Cold agglutinins are antibodies that bind to red blood cells at temperatures below normal body temperature (typically 0–4°C).

Their presence can lead to hemolysis (destruction of red blood cells).

Clinical uses include:

Diagnosing cold agglutinin disease (CAD), a rare autoimmune hemolytic anemia.

Supporting diagnosis of infections such as Mycoplasma pneumoniae and infectious mononucleosis.

Evaluating unexplained anemia, jaundice, or hemolysis.

The test is performed by mixing patient serum with red blood cells and observing agglutination at cold temperatures.

Analyte: Cold agglutinins (usually IgM autoantibodies) in serum.

Normal Result: Negative (no agglutination at cold temperatures).

Abnormal Findings:

Positive test: Indicates presence of cold agglutinins.

High titers: Associated with cold agglutinin disease, hemolytic anemia, or certain infections.

Clinical Use:

Provides evidence of autoimmune hemolysis triggered by cold exposure.

Helps differentiate causes of anemia and hemolysis.

Guides treatment decisions (e.g., avoiding cold exposure, immunosuppressive therapy).