MMSC 420 final exam review 2023 with complete solution
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Course
MMSC 420
Institution
MMSC 420
MMSC 420 final exam review 2023 with complete solution
expected ABO typing results
forward and reverse typing results match
unexpected ABO typing results
-forward and reverse typing results do not match (missing reaction or extra reactions)
-current typing does not match historical records
...
mmsc 420 final exam review 2023 with complete solu
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MMSC 420 final exam review 2023 with complete solution
expected ABO typing results
forward and reverse typing results match
unexpected ABO typing results
-forward and reverse typing results do not match (missing reaction or extra reactions)
-current typing does not match historical records
pre-analytical ABO typing errors
error before ABO typing that leads to discrepancy
-incorrect patient is identified
-incorrect labeling of specimen
-mixing up patients samples
analytical ABO typing errors
errors during ABO typing that leads to discrepancy
-technical error
-clerical error: mixing up tubes, recording results incorrectly
-cell suspension too heavy: post zone causing false negatives
-forgetting to add reagent or serum
-not following SOPs
-uncalibrated centrifuge
-contaminated reagents
-under/ over centrifugation
-improper resuspension of cell button: missing weak reactions
-mixing up patients samples
post-analytical ABO typing errors
things that were done in the hospital that lead to ABO discrepancy
-dilution of antibodies: administering plasma products causes patient's plasma and
antibodies to be diluted and weakly react in reverse type
-transfusion: exchange transfusion/ RBC transfusions can introduce RBCs of a different
ABO type than patient's own cells and lead to forward typing showing 2 cell populations
-plasma expanders: administering albumin or crystalloids causes issues with ABO
typing
-bone marrow/ stem cell transplants: patient's ABO type may not fully convert and ABO
forward and reverse types remain mismatched
determining cause of ABO discrepancies
-suspect weak reactions: look at 1+ reactions, or missing reactions as possible causes
of issues
-review patient's history: ongoing diagnoses, past treatments or infections can help to
determine what discrepancy is occurring
-suspect serum: discrepancy issues are commonly due to weak reacting/ cold reacting
antibodies in the serum
group I ABO discrepancies
unexpected reactions occur in the reverse type due to weakly reacting/ missing
antibodies
-most common type of ABO discrepancy
Resolutions:
,-RT or 4C incubation to enhance IgM antibodies (ABO antibodies)
-increase cell to serum ratio (4 drops of patient's serum instead of 2 gets more antibody
into the mix)
-look at patient history
group I ABO discrepancies causes
-inability/ decreased ability to produce antibodies: newborns, elderly, blood cancers
(leukemia, lymphoma), immunosuppressive therapies, congenital
hypogammaglobulinemia/ agammaglobulinemia, bone marrow transplant recipients
-diluted antibodies: massive transfusion of plasma products dilutes patient's antibodies
-ABO subgroup with antibodies present
group II ABO discrepancies
unexpected reactions in the forward typing due to weakly expressed or missing
antigens
Resolutions:
-RT or 4 C incubation with enzyme enhancement to strengthen antisera reactions with
patient RBCs
-look at patient history
group II ABO discrepancies causes
-2 cell populations: RBC/ exchange transfusions or chimerism (BMT or SCT) lead to
mixed field agglutination with antiseras
-polyagglutinable RBCs: positive reactions with all antiseras
-weakly expressed A or B antigens: old age or disease (hodgkin's lymphoma, leukemia)
-ABO subgroups: react weakly with antiseras
-excess blood group soluble substance (BGSS): due to carcinoma of stomach of
pancreas, neutralizes reagent antiseras and causes all reactions to be negative (wash
cells)
-fetal maternal bleeds
auto control and screening cells
if you run your ABO typing at RT or 4C to enhance reactions, you will have to run
_________________ and _________________ at the same temperature
group III ABO discrepancies
unexpected reactions in ABO typing that occur due abnormal plasma proteins
-rouleaux (coin stacking) can be confused for agglutination and needs to be
differentiated microscopically
Resolutions:
-saline replacement: replace plasma with drops of saline to attempt to disperse rouleaux
(will not disperse if it was true agglutination)
group III ABO discrepancies causes
-wharton's jelly: substance in cord blood that contaminates delivery blood samples,
wash cells
-multiple myeloma
-waldenstom's macroglobulinemia
-hodgkin's lymphoma
-elevated fibrinogen
-plasma expanders
group IV ABO discrepancies
,unexpected reactions in ABO typing due to miscellaneous problems
Resolutions:
-look at patient history
group IV ABO discrepancies causes
-cold reacting autoantibodies
-cold reacting alloantibodies
-bone marrow transplant: patient's ABO type never fully converts and forward and
reverse type do not match
-ABO isoagglutinins
-antibody against low incidence antigen in antisera: antisera shows positive reaction
with patient's RBC due to extra antibody that is in the reagent antisera, not the ABO
antibody (test with another lot #)
A subgroups
-A1: about 80% of type A individuals
-A2: about 20% of type A individuals, usually not detected unless anti-A1 antibody is
produced and causes issues with reverse ABO typing
-weak A subtypes exist, but are extremely rare
A2 subgroup ABO discrepancy
if an individual is type A2 and produces anti-A1 antibody the forward type looks like a
normal A, but reverse type shows antibody against A1 reagent RBCs
Resolution:
-forward type: use anti-A1 lectin with patient's cells, negative reaction
-reverse type: use A2 reagent RBCs in patient serum, negative result
A2 subgroup transfusion
-nonemergency transfusion: crossmatch several units to find A2 blood
-stat situation: transfuse O- or O+
B subgroups
much less common than A subgroups
-acquired B antigen: carcinoma/ infection/ obstruction of the colon causes deacetylation
of type A antigens that makes them react like type B antigens (with antisera) in the
forward type
-weak B subgroups exist but are VERY rare and almost never seen
acquired B antigen ABO discrepancy
acquired B antigen causes the forward type to look like AB, but reverse type looks like
normal A
-autocontrol negative (anti-B antibodies do not agglutinate deacetylated A antigen)
Resolution:
-look at patient history for infection, cancer or obstruction of the colon
bombay (hh) discrepancy
-individuals with no ABO or H antigens on their cells due to inheritance of hh genes
-forward and reverse type look like normal O individual
Resolution:
-entire ABSC/ABID panel will be positive due to anti-H antibody reacting with all type O
reagent cells
-patient cells will not react with anti-H lectin (H antigen is not present)
, anti A-1 lectin (dolichos biflorous)
reagent lectin antisera used in forward type when A subtypes are suspected
-A1 cells: 4+ reaction
-A2 cells: negative reaction
anti-H lectin (ulex europaeus)
reagent lectin antisera used in forward type when A subtype, or Bombay vs. O is
suspected
-O cells: 4+ reaction
-Bombay: negative reaction
-A2: 4+ reaction
-A1: weaker positive reaction
A2 reagent RBCs
reagent RBCs that are used in reverse type if A subtypes are suspected
-A1 individual: strong agglutination if Anti-A2 antibody is present (not always present)
-A2 individual: no agglutination
O reagent screening cells
reagent RBCs that are used to determine if the unexpected reactivity in the ABO
reverse typing is due to a non-ABO antibody
-test patient's serum against a panel of cells to see if another antibody is present
-if another clinically significant antibody is present, this could be the cause of
unexpected agglutination in reverse type (reagent A1 and B cells used in the reverse
type have other clinically significant antigens on them)
ABO discrepancy resolution techniques
-increased incubation time: giving more time for antibodies to bind to RBC antigens
helps produce stronger agglutination in forward and reverse typing
-increased serum to cell ratio: adding 4 drops of patient serum instead of 2 adds more
antibody into the test and helps produce stronger agglutination in the reverse type
-4C or RT incubation: cold temperatures help to increase reactivity of the IgM ABO
antibodies and makes agglutination stronger
-enzyme treatment: makes the antigens on the RBC easier for antibodies to bind to and
leads to stronger agglutination
-adsorption and elution techniques: antibodies adsorbed onto patient's unphenotyped
RBCs and then eluted off and identified help identify what antigens are present on Pt's
RBCs
reference laboratory assistance (ABO discrepancy resolution)
-advanced testing to confirm cases of acquired B antigen
-testing with anti-H lectin (bombay and A subtypes)
-adsorption and elution studies
-weak B subgroup testing
ABO specific transfusion
patient is transfused with RBCs that are the same ABO type as their own cells
ABO compatible transfusion
patient is transfused with RBCs that are not the same as their own ABO type, but will
not cause a transfusion reaction
-e.g. transfusion O RBCs into an A individual
RBC transfusion compatibility
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