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
jslum.com | Medicine
Antiglobulin test (Coombs test) AHG (Antihuman globulin) – produced via animals by injection of human globulin, compleme nt, immunoglob ulin 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 ABO, Rhesus grouping of patient’s blood
Screen Hold Red blood cell antibody Keep screened sample screening until need arise Patient’s serum tested Will not be crossagainst reagent red matched until needed cells (known red cell antigens) Using known red cell antigens (red cell 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 When blood is required, crossantibody matching will be performed (saline, room temperature) Compatible blood will be supplied Blood issued as soon as neede d after full cross-matching & typed Full cross-matched proceed in lab (negative for antigen to particular Blood is taken even when procedure antibody) is not finished Advantages of GSH ↓ Blood stock (for blood cross -matching - n ot needed for blood transfu sion) ↓ 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
Red cell agglutination (incompatible donor) – Test tube, Blood film