Lecture 7 Flashcards
Blood Bank sample requirements
patient’s full name and unique identity number
Writing must be legible and indelible
Date of collection
Sample must be collected within 3 days of scheduled transfusion
initials or signature of the person who collected the sample
Hemolyzed samples
cannot be used for testing
hemolysis caused by activation of complement by antigen-antibody complexes will be masked
To avoid contamination blood
samples should not be taken from intravenous tubing lines
ABO Grouping
the most critical pretransfusion serologic test
Tube tests offer greater sensitivity
Group I Discrepancy
occur between forward and reverse groupings owing to weak or missing antibodies
most common discrepancy
Group I Discrepancy: reason
depressed antibody production
Newborn/elderly
Leukemia (CLL)
Lymphoma
Immunosuppresive drugs
Resolution of Group I Discrepancies
enhance the reverse group reaction
incubating the patient serum with reagent A1 and B cells at room temperature(25ºC) for approximately 15 to 30 minutes
What if Group 1 resolution doesn’t work?
serum-cell mixture can be incubated at 4ºC for 15 to 30 minutes
Group II Discrepancies
Occurs between forward and reverse groupings owing to weak or missing antigens
Group II Discrepancies: Causes
Subgroups of A and/or Subgroups of B being present
Leukemias
Hodgkin’s disease
Acquired B” Phenomena
Antibodies to low incidence antigens
Group II resolution: Possible weak subgroup of A
Test cells with anti-A,B reagent
Test with Anti-A1 lectin
May require genotype testing to confirm
Group II resolution: Possible acquired B
Treating red cell with acetic anhydride re-acetylates the surface molecules
Group III Discrepancies
Occurs due to protein or plasma abnormalities
Group III discrepancies: Causes
Elevated globulin levels like:
Waldenstroms macroglobulinemia
Multiple Myeloma
Hodgkin’s disease
Rouleaux due to elevated Fibrinogen
Wharton Jelly
Group III discrepancies: Resolution
Cells must be washed to alleviate problem
Group IV discrepancies
Polyagglutination-spontaneous RBC Agglutination
Bacterial contamination
Warm autoantibodies
Presence of warm autoimmune antibodies. Most common
reactive at 37o C
Cold autoantibodies
anti-I and anti-H and anti-IH
Benign cold reacting autoantibodies are present in all normal human sera
Resolution to Group IV Discrepancies
If the poly agglutination is suspected, lectin studies should be performed
Potent Cold Autoantibodies
○ cause spontaneous agglutination, causing positive Coomb’s test (DAT)
resolved by incubating red cells at 37C for a short period of time
Warm Antibodies
When expected of causing a false positive reaction in the forward grouping the cells can be treated to a gentle heat elution at 45C for the cells to be reliably typed
Unexpected ABO isoantibodies
react at room temperature with the corresponding antigen present on the reagent cells
A2 and A2B individuals: produceanti-A1, or A1
A1B: produce anti-H
Unexpected Alloantibodies
may cause a discrepancy in the reverse grouping
In this situation- a panel should be performed with the patient’s serum
Cis-AB
inheritance of both AB genes from one parent carried on one chromosome and the O gene inherited from the other parent
results in the offspring inheriting three ABO genes
Rh Grouping
performed using anti-D blood grouping serum
Rh Controls must be run alongside, to avoid incorrect designation of Rh-negative patients as Rh-positive
If the Rh-control is positive?
Rh grouping test is invalid and must be rerun
DAT should be performed to determine whether autoantibodies is responsible for the positive Rh control
If Rh group of the recipient cannot be established and transfusion is essential
Rh-negative blood should be given
Antibody Screen
The patient’s serum or plasma must be tested for unexpected antibodies
Antibody Screen offers several advantages over direct crossmatch testing
group O red cells that are known to carry optimal representation of important blood group antigens
Testing can be performed well in advance of the anticipated transfusion
Antibodies regarded as always being potentially clinically significant
ABO, Rh, Kell, Duffy, Kidd, SsU
Antibodies that may sometimes be clinically significant
Lewis (Lea), MN, P,1 Lutheran (Lua, Lub), Cartwright (Yta)
Rarely seen antibodies that are clinically significant
Leb, Chido/Rogers (Cha/Rga), York (Yka), Sda, Xga
Crossmatch Testing
testing of the patient’s serum with the donor cells
“compatibility test”
Two main functions for performing the crossmatch
a final check of ABO compatibility between donor and patient
may detect the presence of an antibody in the patient’s serum that will react with antigens on the donor RBCs that was not detected in the antibody screening
Crossmatch Testing: Results
A jagged or firm button edge is indicative of a positive reaction = incompatible
smooth swirling of free cells off the RBC button indicates a negative reaction = compatible
Whenever the crossmatch test result is positive
results of the autocontrol and antibody screening test should be reviewed
Causes of positive results in the serologic crossmatch
Incorrect ABO grouping of the patient or donor
Resolution - Repeat testing
