7. ABID & problem resolution Flashcards
Antigens represented on screening cells
D, C, E, e, c
M, N, S, s
P1
Lu a/b
K, k
Fy a/b
Jk a/b
advantages of ABS (3)
advance warning of XM problems
time to find compatible blood before critical point
clarify problems in ABO/Rh testing
limitations of ABS (3)
only 2-3 cells
some antigens not homozygous
some antigens not represented at all
ABS+ may indicate… (3)
alloAb
autoAb
anomaly
used to rule out autoAb
autocontrol
DAT
Autocontrol + at IS (2)
cold autoAb
rouleaux
Autocontrol + at AHG (2)
warm autoAb
trxn
examples of anomalies (5)
rouleaux
fibrin
wharton’s jelly
imperfections in surface of tube
Ab to test component (PEG, gel, dye)
when is DAT performed? (4)
after trxn
after HDFN
after ABS+
Dr orders
what happens after ABS+? (2)
ABID panel
DAT
very first procedures after getting ABS+ (2)
call floor to let them know there will be a delay
obtain pt hx (transfusion, dx, medications, pregnancy hx, age)
ABID STEPS (7)
- rule-outs
- decide possibles
- decide probables
- use Fisher’s exact test to confirm probables
- eliminate other possibles
- perform Ag typing on pt cells
- XM units negative for clinically significant Ab
factors used to determine probables (4)
- pattern of reactivity
- phase/temp
- dosage
- enzyme treatment
IS/cold Abs (4)
Lewis
MN
P1
Lua
AHG/warm Abs (6)
Rh
Kell
Fy
Jk
SsU
Lub
Marked dosage (4)
MNS
Jk
Fy
some Rh
No dosage (5)
D
Kell
Lutheran
P1
Lewis
Destroyed by enzymes (2)
MN
Duffy
Enhanced by enzymes (4)
Rh
Jk
P1
Lewis
Enzymes have no effect (2)
Kell
SsU
probables must have ——– to ensure results are not due to chance
p-value ≤ 0.05
Fisher’s exact test
3 positives
3 negatives
how to select cells to eliminate possibles
negative for probables
homozygous for possible
OR 3 heterozygous for possible
never ruled out heterozygously
Kidd
can resolve ABID problems using —- or —- to denature IgM
DTT
2-ME
↑ anti-M
acidify plasma
neutralization can help in ABID of…
Lewis
P1
Sda (urine)
used to resolve interfering known antibodies in ABID
auto or allogeneic adsorption techniques
Ag typing ensures…
consistency of ABID results
+ control in Ag typing should be…
why?
heterozygous
ensures that the test detects the weakest potential expression of antigen
QC is run how often for Ag typing?
every day of testing
how to select # of units to screen
units needed / proportion compatible
most discrepancies result from ——–
why we need…
tech error
well-written, meticulously followed testing procedures
first attempt at resolving a discrepancy problem
repeat testing with washed cells
often a clue to expect rouleaux
multiple myeloma
eliminate fibrin (2)
dissolves at 37°
dissolved by protamine sulfate
Hodgkin lymphoma
decreases antigen expression
eliminate high titer A or B substance in serum
wash
test saliva
increases reactivity of ABO abs
RT incubation
2 lectins used to ID subgroups
A1 lectin —reacts with A1 cells
H lectin —helps detect bombay
anti——– may help get a stronger forward rxn with subgroups
anti-A,B
causes of unexpected forward type results (5)
- cold autoAb or alloAb
- Ab to dyes
- Acquired B antigen
- rouleaux or wharton’s jelly
- transfusion/transplantation
resolve cold Ab giving discrepant forward results (2)
warm saline wash
DTT (denatures IgM)
resolve Ab to dyes giving discrepant forward results
wash
resolve acquired B antigen giving discrepant forward results (2)
repeat with monoclonal, acidified anti-B
autocontrol —anti-B in reverse type does not react
explain acquired B
caused by GI disturbance (malignancy, obstruction, GN septicemia)
N-acetylgalactosamine is cleaved to give galactosamine
mistaken for D-galactose by some reagents
resolve wharton’s jelly
wash 4x
what do you do after getting an MF rxn?
pt hx check
causes of unexpected reverse type results (7)
Patient
- Age, young or old
- Immcomp disease states
- Transfusion
Test system
- AutoAb or alloAb
- ABO subgroup
- Prozone
- Rouleaux
resolve low Ab titer (age) giving discrepant reverse results (4)
incubate RT 15-30 mins
incubate 4° 15-30 mins
add O plasma to system as control
if forward type is O, add anti-A,B
resolve ABO subgroups giving discrepant reverse results
test with 3 A1 and 3 A2 cells
3 A1 and 3 A2 all + means…
acquired anti-A via transfusion
interferes with testing after transfusion
CD47
resolve prozoning giving discrepant reverse results
dilute serum
resolve auto/allo Ab giving discrepant reverse results (3)
cold autoadsorption
prewarm technique
ABID; retest with segments of units = for antigen
causes of Rh false negatives (5)
- incorrect reagent/forgot reagent
- reading error
- heavy cell suspension
- undercentrifugation
- CML (interferes with Rh)
causes of Rh false positives (5)
- DAT+ (autoAb)
- rouleaux
- polyagglutination
- incorrect reagent
- overcentrifugation
EGA
EDTA glycine acid
EGA purpose
dissociates bound Ab from cells, leaving cells intact
inactivates Kell
used to get accurate weak-D when DAT+
A2 discrepant test results (2)
anti-H 2+
A1 reverse 0-2+
A3 discrepant test results (4)
anti-A: 2+mf
anti-A,B: 2+mf
anti-H: 3+
A1 reverse: 0-2+
Ax discrepant test results (5)
anti-A: +/=
anti-A,B: 1-2+
anti-H: 4+
A1 reverse: 0-2+
no A substance in saliva
B3 discrepant test results (3)
anti-B: 1+mf
anti-A,B: 2+
anti-H: 4+
Bx discrepant test results (4)
anti-B: +/=
anti-A,B: 0-2+
anti-H: 4+
no B substance in saliva
