From the Research
Cold Agglutinin Test Results
- The Cold Agglutinin (CA) test can be positive or negative, depending on the presence of cold-reactive autoantibodies in the patient's blood 1.
- A study found that 98% of patients with a negative direct antiglobulin test (DAT) using anti-C3 had a negative CA titer (<64), suggesting that a negative DAT can rule out elevated CA titers and the diagnosis of Cold Agglutinin Disease (CAD) 1.
- However, there are cases where the CA test can be positive even with a negative DAT, as seen in a patient with a non-complement-activating IgG1 kappa cold antibody with Pra specificity 2.
- Another study found that nearly all cold agglutinins are positive for the C3d direct antiglobulin test (DAT), and a negative C3d DAT should prompt investigation of a possible warm AIHA 3.
Factors Affecting Test Results
- Temperature control of specimens is crucial in blood testing for Cold Agglutinin Disease, as cold agglutinin titer, IgM quantification, electrophoresis, and immunofixation methods may produce false-negative results if the serum is not temperature-controlled at 37-38°C until serum separation 4.
- The type of antibody present can also affect test results, with IgM warm autoantibodies being more commonly associated with Cold Agglutinin Disease 5, 3.
- The use of different testing methods, such as the dual antiglobulin test (DDAT), can help identify weak or nonagglutinating RBC-bound IgM warm antibodies 5.