Cold autoantibodies usually cause a positive DAT due to complement (commonly C3d) coating the red cell surface.
Strategies to determine if a cold antibody is clinically-significant:
Incubate patient serum with normal red cells suspended in saline at room temperature for 30-60 minutes. A negative test practically rules out a clinically-significant cold antibody.
If the screening test is positive, further tests are necessary:
Antibody titration (clinically-significant cold agglutinins usually have a titre of 1:500 – 1:1000 at 4°C).
Thermal amplitude: antibodies active at >30°C (detected by tube NISS direct agglutination) are usually clinically-significant.
Samples should be transported to the lab at 37°C. If this is not possible, then EDTA samples should be warmed to 37°C for one hour prior to testing.
Cold antibodies may agglutinate all cells within the reverse ABO group, leading to discrepant ABO typing.
Because the antibody is a cold-reacting IgM, patient red cells can be washed at 37°C to remove the IgM autoantibody.
For antibody screening, separately pre-warming patient plasma and screening red cells to 37°C before the IAT can avoid the non-specific reactivity of the cold autoantibody.
For potent, cold-reacting antibodies active at 37°C:
The patient’s plasma can be treated with DTT, which disrupts the J chain of the IgM antibody. Post-DTT-treated samples should then be tested at 37°C by IAT technique using a monospecific IgG antiglobulin rather than a polyspecific one.
Why would someone choose to do a DTT over a cold alloadsorbtion? In my lab we have access to both techniques.
I know DTT is quicker, but the plasma is only valid for 24 hours after treatment. Vice versa for alloadsorbtion.
I’m UK based, if that makes any difference.
Normal red cells in the 1st sentence refer to patient rbc or reagent rbc?
Reagent
Is Cold auto antibody can be enhance by enzymes?
Why would someone choose to do a DTT over a cold alloadsorbtion? In my lab we have access to both techniques.
I know DTT is quicker, but the plasma is only valid for 24 hours after treatment. Vice versa for alloadsorbtion.
I’m UK based, if that makes any difference.
Many thanks for any help 🙂 🙂
Is a cold agglutination they same thing as a cold autoantibody?