Weak D Testing and Rh Antigens

These flashcards cover key concepts related to the Weak D test, Rh antigens, and their implications in transfusion medicine.

Weak D test

A test performed to accurately identify the D antigen status in patients and donors, especially when the antigen expression is too low for standard testing.

Rh positive

Label given to weak D positive patients or donors, indicating the presence of D antigen, allowing safe transfusion.

Weak D mechanisms

Three mechanisms include Genetic Weak D, C-trans (Position Effect), and Partial D (Mosaic).

IgG antibody

Type of antibody that the Rh antibody is classified as, unlike ABO antibodies which are primarily IgM.

Warm-reacting antibodies

Antibodies that exhibit clinical significance at physiological temperatures, specifically at 37°C.

Hemolytic Transfusion Reaction

A reaction caused by Rh-positive blood given to a patient with anti-D, leading to extravascular hemolysis.

Rh immune globulin (RhIG)

A treatment given to Rh-negative women during pregnancy to prevent alloimmunization by clearing fetal Rh-positive cells.

Complement binding

Rh antibodies generally do not efficiently fix or bind complement, leading to extravascular hemolysis.

Fisher-Race system

One of the phenotyping systems for Rh antigens, labeling them as D,C,c,E,e.

Rh null phenotype

A rare condition where individuals lack all Rh antigens (D, C, c, E, e) on their RBCs.

Antihuman Globulin (AHG) test

A test using antihuman globulin to detect IgG antibodies or complement on RBCs that wouldn’t normally show agglutination.

Check cells

Reagent RBCs that have been coated with IgG and are used to validate the AHG test results.

Positive DAT

Indicates that RBCs are coated with IgG or complement in vivo, meaning inside the patient's body.

Positive IAT

Indicates that IgG antibodies in the patient's serum have successfully attached to reagent RBCs in vitro.

Rh antigen inheritance

Rh antigens are inherited as codominant alleles from each parent organized as haplotypes.