Antiglobulin Antiglobulin test ( Coombs Coombs test)
Compatibility testing Prevent haemolysi
AHG (Antihuman globulin) – produced via animals by injection of human globulin, complement, complement, immunoglobulin immunoglobulin AHG + Human RBC (coated with Ig antibody) or complement Aggl utination utination – i ndicate +ve test Donor’s blood is not compatible/ safe for transfusion
Blood grouping Reagents/ equipments equipments Anti A, B, AB (direct (direct g rouping) Blood from recipient (cells, serum) Tile, Test tubes Centrifuge Known cells – O, A, B (indirect grouping)
AHG enhance red cell ag glutination (red (red cells coated by antibodies)
Cross Matching (GXM) To tra nsfuse nsfuse compatible compatible r ed cells to pati ent Principle Red cells from donor (same (same ABO, R hD) tested against recipient (patient) serum Aggluti nation nation – incompatible incompatible donor red cells Methods Detecting clinically significan significantt IgM antibodies (cold) (cold) – saline in room temperature Detecting clinically significan significantt IgM, IgG antibodies (warm) (warm) – saline 37°C Detecting immune antibodies (mainly IgG) – indirect antiglobulin test (AHG test) at 37°C
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 reagen reagentt r ed cells (known red cell antigens) Using known red cell antigens (red cell panel I, II, III) – i ndirect Coomb’s Coomb’s test t est
Will not be crossmatched until needed
Cross matching test
+ve result will show agglutination (indicate (indicate patient has specific antibody(s) to antigen(s)) Results of antibody screening Postive Postive (+ve) Identify antibody – type of red cell antibody
Red cell antibodies to Minor blood gr oups Lewis, Duffy, Kell antigens (on red cell surface) • Major blood gr oups ABO, Rhesus D antigen (very immunogenic) Development of Red cell antibodies by Naturally Immune Immune me chanisms •
Compatible blood will be supplied after full cross-matching & typed (negativ (negativ e for antigen to particular antibody)
Negative (-ve) When blood is required, crossmatching matching w ill be performed performed (saline, room temperature) Blood issued as soon as needed Full cross-m cross-matched atched 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 (equal t o doing GXM) Blood is delivered ASA P when 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 for r ed cell antibody antibody screening No history of recent blood transfusion
Gel card met hod GXM & GSH AHG is pre-added in gel card column Agglutination show as layer of red cells on top of gel column
Red cell agglutination (incompatible donor) – Test tube, Blood film
