Unit 7: Investigation of a Positive DAT

When performing a DAT, what tube must be used for collecting samples?

EDTA

What are the steps of performing a DAT?

1. polyspecific DAT - IS, RT, AHG, CC

If polyspecific DAT is +:

1. monospecific IgG - IS, AHG, CC

2. monospecific C3 - IS, RT, AHG

Transfusion reactions would have a + DAT for (IgG/C3).

IgG

All phases of AHG being reactive due to IgG (sometimes C3) is seen in:

warm autoimmune disease

Cold autoimmune disease and pneumonia react with all cells at colder temperatures due to (IgG/C3).

C3

A clotted tube stored at 4C will have a positive DAT due to (IgG/C3).

C3

A weak and MF positive DAT is seen in:

transfusion reactions

How do you identify the antibody causing a positive DAT during a transfusion reaction?

eluate (patient RBCs + chemical)

Positive DATs are associated with what kind of diseases?

autoimmune diseases (systematic lupus erythematosus (SLE), infectious mononucleosis (IM), pneumonia, cold agglutinin syndrome (CAS))

A positive DAT with non-reactive serum and eluate is seen in:

positive DAT due to medication

What medication can mimic a warm autoantibody reaction?

methyldopa

What is the purpose of performing an elution?

determine if + DAT is due to:

1. alloantibody

2. autoantibody

3. drug

When kind of antibodies can we perform and elution on?

IgG antibodies

What is the principle of an elution?

method that removes antibodies from sensitized patient RBCs, creating an eluate that can be used for antibody identification

A positive DAT due to an (autoantibodies/alloantibodies) is usually stronger and is not MF.

autoantibody

What type of history would tell us that a patient does NOT have an alloantibody?

has NOT received transfusion in the past 3 months

(Autoantibodies/Alloantibodies) will mask (autoantibodies/alloantibodies).

autoantibodies will mask alloantibodies

How do we remove autoantibodies that are masking alloantibodies?

adsorption

Mixing patient cells with their own plasma so autoantibodies are removed from their plasma, leaving only alloantibodies is known as an:

autoadsorption