Rh TYPING and WEAK-D TESTING

Rh System

It is the second most important blood group system in immunohematology?

Over 60

Rh system is composed of how many different antigenic specificities?

Rh antigen, Rh antibodies

Unlike the ABO system, the presence of this antigen on the RBCs and these antibodies in the serum does not have an inverse relationship.

Rh antibodies

IgG

Transfusion/ Pregnancy

These antibodies are considered immune antibodies; they are ___ in nature; and the formation of these antibodies requires prior exposure through ___?

• D, C, c, E, e

what are the 5 antigens of the Rh Blood Group?

d antigen

This antigen doesn’t exist and is only an indicator of the absence of the Capital D antigen.

D antigen

This is the only antigen tested in Rh Blood Typing

Anti-D IgG

It is colorless and is added directly to red cell suspension

Presence and absence of D-antigen on a surface of a red blood cells using commercially prepared anti-D antisera.

Rh Typing Principles

By mixing Anti-D antisera plus blood sample on a slide/tube, mix then observed for the presence of agglutination reaction.

The detection of Rh status is done by?

• Direct Typing

• Indirect Typing

2 METHODS OF ANTIGLOBULIN TEST:

Indirect Typing/ Weak-D Testing

Confirmatory Test for Rh typing?

Rh Positive

Rh Negative

Indicates that there is/are presence or absence of the D antigen on the patients RBCs

Type AB+ (positive)

This indicates that the patient’s ABO group is AB and that the D Antigen is present

Type O- (negative)

This indicates that the patient’s ABO group is O and that D antigen is absent

Weak D Testing

This serves as an application of IAT (Indirect Antiglobulin Testing) and is performed to determine the presence of weak D antigens

1. Genetic

2. Position Effect

3. Partial D or D mosaic

The 3 mechanisms of Weak D

Genetic

A mechanism of weak D where there is a mutation in the Rh D genes

Position Effect

A mechanism of Weak D where it involves the insertion of the Rh D gene into atypical genomic locations leading to altered chain expression patterns—and may influence the transcription and translation processes affecting the quantity and quality of D-antigen produced

Partial D / D Mosaic

A mechanism of weak D that arises from genetic alteration that results in the production of structurally altered D-antigen proteins.

• The tube is incubated at 37C

• Wash 3 times

• AHG is added

• Interpret results

  • Macroscopic

  • Microscopic

How to perform weak D testing?

Rh Typing

Determines the presence and absence of D antigen

Only D antigen is tested

Slide Method

Considered as a screening test

Results of this method is not final; it should always be confirmed with Tube Method

Tube Method

Considered as a confirmatory test

It confirms the initial results of the Rh slide typing

The gold standard in Rh Typing