MMSC 420 Exam 1 UPDATED Exam
Questions and CORRECT Answers
expected ABO typing results - Correct Answer- forward and reverse typing results match
unexpected ABO typing results - Correct Answer- -forward and reverse typing results do not
match (extra reactions, missing reactions)
-current typing does not match historical records
pre-analytical errors (ABO discrepancy) - Correct Answer- errors occurring before patient
sample is tested that lead to ABO discrepancy
-incorrect identification of patient
-incorrect labeling of specimen (labeling needs to occur at the patient bedside)
-patient's samples mixed up
analytical errors (ABO discrepancy) - Correct Answer- errors that occur during testing that
lead to ABO discrepancy
-technical errors
-clerical errors: mixing up tubes, writing down results incorrectly
-cell suspension too heavy: beyond 2-5% there is post zone effect
-failure to add reagent of patient serum
-failure to follow instructions or standard operating procedures: e.g. letting incubation go too
long
-failure to note hemolysis: always a positive reaction
-uncalibrated centrifuge
-contaminated reagents
-under/ over centrifugation
-improper resuspension of cell button: miss weak reactions
-confusing patient samples
, post-analytical errors (ABO discrepancy) - Correct Answer- things that were done in the
hospital that lead to ABO discrepancies
-dilution of antibodies: administering plasma products causes patient's own plasma and
antibodies to become diluted and react weakly in reverse type
-exchange transfusion/ RBC transfusion: introducing RBCs that are not the same ABO type
as the patient cause forward typing to show 2 cell populations
-plasma expanders: administering albumin or crystalloids causes issues with ABO typing
-bone marrow/ stem cell transplant: patient's ABO type might not fully convert and lead to
ABO typing discrepancies
determining cause of ABO discrepancies - Correct Answer- -suspect weaker reactions: look at
1+ reactions, or missing reactions as the first sign of an issue
-review patient's history: ongoing diagnoses, past treatments, or infections can help to clue in
what is going wrong
-suspect the serum: discrepancy issues are commonly due to weak reacting, or cold reacting
antibodies
group I ABO discrepancies - Correct Answer- Unexpected reactions occur in the reverse type
due to weakly reacting or missing antibodies
-*most common type of ABO discrepancy*
-forward typing is normal
-resolutions: RT or 4C incubation to enhance IgM ABO antibodies, increasing cell to serum
ratio (4 drops of patient serum instead of 2 to get more antibody in the mix), look at patient
history
group I ABO discrepancies causes - Correct Answer- -inability/ decreased ability to produce
antibodies: newborns up to 6 months, elderly, leukemia or lymphoma with
agammaglobulinemia, immunosuppressive therapies, congenital hypogammaglobulinemia/
agammaglobulinemia, bone marrow transplant recipients
-diluted antibodies: massive transfusion of plasma products dilutes patient's antibodies
-ABO subgroups (if antibodies are present)
group II ABO discrepancies - Correct Answer- unexpected reactions in the forward typing
due to weakly expressed or missing antigens
-reverse type is normal
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