Identification of unexpected antibodies

State the purpose and method of the autocontrol when performing an antibody screen

Mix pateint’s serum and RBCs together to test for autoagglutination

When your autocontrol is positive what is the next step?

To perform a DAT to determine if autoantibody or alloantibody is present

Differentiate alloantibodies and autoantibodies based on autocontrol and DAT test results

• An autoantibody may be present if the autocontrol and DAT is positive.

• An alloantibody will not cause positive autocontrol. Panreactivity with all cells (except autocontrol may suggest alloantibody to a high-frequency antigen)

Describe the impact of dosage on antibody identification

Dosage is when an antibodies react differently with cells that have homozygous versus heterozygous antigen expression

Weaker reaction- heterozygous cells

Stronger reaction- homozygous cells

Describe the purpose of the p-value

The p value helps determine the likelihood that the correct antibody has been identified using an antibody panel

p-value should be less than ___?

0.05

What is the p-Value formula?

Anti-Fya identified:

• 4 positive cells

• 6 negative cells

• 10 total cells

Calculate the p-Value

4! X 6!         24 x 720

-------- = ---------------- = 0.0048

   10!         3,628,800

How are enzyme treated cells used in antibody identification?

Cell panels that come pre-treated with ficin or papain

Adds evidence/clarifies reaction patterns, especially in patients with multiple Ab’s

What is neutralization and how is it used in antibody identification?

Neutralization: Inactivation of antibody by combining it with soluble form of corresponding antigen

Helps uncover underlying antibodies by uncovering the neutralized one was ‘hiding’

What is Elution and how is it used in antibody identification?

Elution: Chemically frees antibodies bound to red blood cells while maintaining structure

• Uses:

• Helps ID antibody(ies) from Positive DAT

• Concentrate antibody to help identify weakly reactive antibodies/antigens

• Prepare DAT negative cells for more tests

• Combine with adsorption to remove one antibody when multiple are present

• Can be used to detect a weakly reactive antigen, such as an ABO subgroup

What is Adsorption, and how is it used in antibody identification?

Adsorption- To remove antibodies from plasma

What is Titration and how is it used in antibody identification?

Titration: Measure the strength (concentration) of antibody

Used in determining antibody activity and potential severity of HDFN in alloimmunized pregnant women

State the four most likely causes of all or most cells reacting in an antibody identification procedure

Potential Causes:

• Multiple antibodies

• Antibodies to high-incidence antigens

• Warm autoantibodies

• Cold agglutinins