Chapter 8 Flashcards
Landsteiner was the first too
perform ABO testing
Ottenberg stressed the important of
crossmatch before transfusions
When are cold reactive antibodies significant?
Hypothermia
Dropping OR Temp
Alloantibodies that react at 37 degrees/AHG are capable of
causing decreased survival of transfused RBCs
Alloantibodies are formed by
exposure to foreign RBCs by previous transfusion and/or pregnancy
When are alloantibodies clinically significant?
When they cause HTR or HDNF
What is the purpose of AHG testing?
To detect RBCs sensitized by IgG alloantibodies, IgG autoantibodies, and/or complement
How does the AHG reagent work?
Any cells coated with antibody will be complexed with AHG, and clumps will form (macro or microscopically)
What are the two type of AHG tests
Direct Antiglobulin Test (DAT)
Indirect Antiglobulin Test (IAT)
Polyspecific AHG reagent contains
anti-IgG and and anti-C3d (complement)
Monospecific AHG reagent contains
EITHER
anti-IgG or
anti-C3d
This test detects in vivo sensitization of RBCs w/ IgG and/or complement (like a snapshot of what is happening in the body right now )
Direct Antiglobulin Test (DAT)
This test detects in vitro sensitization of RBCs (like a what if scenario)
Indirect Antiglobulin Test (IAT)
The DAT test is used for
HDN
HTR
AIHA
The IAT test is used for
Compatibility testing, antibody screen, antibody ID, RBC phenotyping
Coombs control check cells usually have avery potent anti-___.
anti-D
What are Coombs Control Cells used for?
To ensure that AHG was not accidently omitted or inactivated.
If CCC cells are negative the test is
invalid and must be repeated
What is a major crossmatch?
Testing a recipient serum against donor RBCs
What is a minor crossmatch?
Testing of the recipients RBCs against donor serum.
NO LONGER PERFORMED (per AABB standards)
What are the elements of Pre-transfusion testing?
ABO Forward Rh ABO Revese Antibody Screen Crossmatch
Gel technology require serum/plasma?
Plasma
Tube testing works better with serum/plasma?
Serum
What can be used to break up small clots from anticoagulated patients on heparin?
Thrombin or protamine sulfate
What must be included on the label of patient blood samples?
2 uniques identifiers Date of Collection Phlebotomists name/ID Legible Indelible Ink if handwritten
Which antibodies are known to cause hemolysis?
ABO P Lewis Kidd Vel
Lipemic blood samples may be
rejected
How long can a blood sample be pre-transfusion tested before the transfusion?
3 days if:
The patient has been transfused in the last 3 months
The patient has been pregnant in the last 3 months
The history is uncertain or unavailble
Blood samples should be stored after a transfusion
1-6 degrees C for a minimum of 7 days after transfusion along with segments
Reviewing previous records for previously detected antibodies helps in avoiding
amnestic response
possible delayed hemolytic sequellae
What is the goal of the antibody type and screen?
To detect antigen-antibody interaction
What is GEL negative and GEL positive?
Negative: button of cells at the bottom
Positive: clump of cells at the top
1+, 2+, 3+ in middle
What is microplate positive and negative?
Negative: no adherance
Positive: Adherance to cell wall
What type of technolody do microplates use?
Solid phase technology
What types of reagents should be used for Rh control?
Commerical Rh control
6% albumin
The Rh control should always be positive/negative
Negative
Why is an Rh control necessary?
To ensure a spontaneous agglutination that could yield a false positive is not present
The combination of screening cells used must contain antigenic expressions of
D, C, c, E, e, K, k, P1, M, N, S, s, Le^a, Le^b, Jk^a, Jk^b, Fy^a, Fy^b
Why do some labs not do the IS reading or room temperautre reading?
Antibodies found in these phases tend to be of no clincial signifiance
What is the risk of not reading after the 37 degree incubation?
Clinically signifianct antibodie in the Rh system might be missed
If CCC are negative, what are some possible causes?
Protein is present
You forgot to add the reagent
Inactive vial of AHG reagent
If the antibody screen is negative, what is the likely hood the crossmatch will be compatible?
Over 99%
What is CMV safe blood and when is it used?
Leukocyte reduced
Used in lung transplant patients
Patients undergoing a bone marrow transfusion require irradiation to prevent
graft-vs-host disease
Patients who experience febrile transfusions reactions may benefit from
leukoreduced blood
If Rh negative units are not available for a patient, you may give Rh+ and
RhoIg shot
what is an autologous donor?
A patient that donates for his/her own surgery
What is an allogenic donor?
Blood that comes from the general population
Order of transfusion donation
Autologous
ABO/Rh compatible directed donor
Allogenic
What percent of labs use IS crossmatch? What percent use IAT?
51% use immediate spin
48% use IAT
When a serological crossmatch is performed, the donor blood used for testing must be taken from
an integrally attached segment of the donor unit
When ca you use the IS crossmatch?
When the antibody screen is non-reactive
No history of unexpected antibodies
If there is no reaction during IS crossmatch the unit is
compatible
What are some reasons for an incompatible (agglutinating) crossmatch?
Unit may be BO incompatible
Rouleux
Auto/alloantibodies
Tube contamination
What are some reasons for an incompatible (agglutinating) cross match if ANTIBODY SCREEN IS NEGATIVE?
Alloantibody in recipient to low incedence antigen on donor RBCs Positive AHG on donor RBCs ABO error Contaminant Polyagglutinable donor RBC
What are some reasons for an incompatible (agglutinating) cross match if ANTIBODY SCREEN IS POSITIVE?
Alloantibody direct roward antigen on donor RBC
Contaminant
What are some reasons for an incompatible (agglutinating) cross match if ANTIBODY SCREEN IS POSITIVE and AUTOCONTROL POSITIVE?
Alloantibody present in recipient who has been transfused
Auto/allo antibody in patient serum
Rouleux
IAT may be performed on patients who demonstrate
clinically significant antibodies
Approximately 1/3 of potention hemolytic alloantibodies are not detected after
5 years
If you must transfuse incompatible blood in dire emergency and you cannot determine antibody ID you must
Medical director and physician decide
Give “least incompatible” by AHG testing
Watch patient
Since naturally occuring anti-A and anti-B are not demonstrated until 6 months, infants do not require
Reverse typing
If enough sample is not collected from an infant, an antibody screen may be performed on
maternal sample
If an antibody screen is negative, additional testing is not necessary for an infant if
Group O cells are used for transfusion
If an infant has a negative antibody screen, but recieves blood other than type O you must
run an intial crossmatch the include IAT
If an infant antibody screen is positive
you must identify and give antigen negative blood
In infants, it is important to crossmatch with blood that has a
stong antigenic expression
To transfuse, their must be two determinations of the recipients ABO group, and one determination must be
performed on a current sample
Ideally, 2 seperate ABO determinations are
performed by two different individuals
The type and screen is ___% effective in preventing the transfusion of incompatible blood.
99.99%
What is the frequency of an incompatible IAT crossmatch?
0.06-0.08%
What is the Maximum Surgical Blood Order?
list of an institution’s surgical procedures and the corresponding blood usually available for a particular surgery. Represents a maximum blood order (not a minimum).
THE MSBOS allows transfusion services to monitor
The ration of crossmatches performed to transfusion givin (C/T) ration
What is a Blood Utilization Review?
transfusion committee performs review of transfusion practices. Audits in current time (prospective view), previous 12-24 hours time (concurrent audit), and days to months after transfusions (retrospective audit)
What is the definition of a Massive Transfusion?
the total blood volume of an individual has been replaces with donor blood within 24 hours
Massive transfusions diminish the purpose of
crossmatch
After a massive transfusion, you must continue to give previous antigen nagative blood because
a secondary response will be rapid for antibody production
In an emergency, if Type O- blood is given without compatibility testing, the unit must be labeled
clearly that pretransfusion testing was not complete at the time of issue