GXM & GSH

Compatibility testing

Prevent haemolysis

Blood grouping

Reagents/ equipments Anti A, B, AB (direct grouping)

Blood from recipient (cells, serum)

Tile, Test tubes

Centrifuge

Known cells – O, A, B (indirect grouping)

Principle Antigen-antibody reaction causes RBC agglutination

Cross Matching (GXM)

To transfuse compatible red cells to patients

Principle

Red cells from donor (same ABO, RhD) tested against recipient (patient) serum

Agglutination – incompatible donor red cells

Methods

Detecting clinically significant IgM antibodies (cold) – saline in room temperature

Detecting clinically significant IgM, IgG antibodies (warm) – saline 37°C

Detecting immune antibodies (mainly IgG) – indirect antiglobulin test (AHG test)

at 37°C

Cross matching test

Red cell antibodies to

Minor blood groups

• Lewis, Duffy, Kell antigens (on red cell surface)

Major blood groups

• ABO, Rhesus D antigen (very immunogenic)

Development of Red cell antibodies by

Naturally

Immune me chanisms

Red cell agglutination (incompatible donor) – Test tube, Blood film

Antiglobulin test (Coombs test)

AHG (Antihuman globulin) – produced via animals by injection of human globulin,

compleme nt, immunoglobulin

AHG + Human RBC (coated with Ig antibody) or complement

Agglutination – indicate +ve test

Donor’s blood is not compatible/ safe for transfusion

AHG enhance red cell agglutination (red cells coated by antibodies)

Group Screen Hold (GSH)

Group Screen Hold

ABO, Rhesus grouping

of patient’s blood

Red blood cell antibody

screening

Keep screened sample

until need arise

Patient’s serum tested

against reagent red

cells (known red cell

antigens)

Will not be cross-

matched until needed

Using known red cell

antigens (red cell panel

I, II, III) – indirect

Coomb’s test

+ve result will show

agglutination

(indicate patient has

specific antibody(s ) to

antigen(s))

Results of antibody screening

Postive (+ve) Negative (-ve)

Identify antibody – type of red cell

antibody

When blood is required, cross-

matching will be performed

(saline, room temperature)

Compatible blood will be supplied

after full cross-matching & typed

(negative for antigen to particular

antibody)

Blood issued as soon as neede d

Full cross-matched proceed in lab

Blood is taken even when procedure

is not finished

Advantages of GSH

↓ Blood stock (for blood cross -matching - not needed for blood transfusion)

↓ Blood wastage & Expiry date

Safe blood is supplied to patients (equal to doing GXM)

Blood is delivered ASAP when needed

Indications for GSH

Cases of elective surgery (chances of not using is ↑ than using blood)

Blood request is not more than 2 units

Adult cases only

Negative for red cell antibody screening

No history of recent blood transfusion

Gel card method

GXM & GSH

AHG is pre-added in gel card column

Agglutination show as layer of red cells on top of gel column

jslum.com | Medicine