MIDTERM LABORATORY L1: WEAK-D TESTING Flashcards
test performed when Rh result is negative
weak-D testing
phenotype of individuals with weak-D
Du type
is Du type considered Rh positive or negative?
Rh positive
3 common mechanisms of weak-D
Genetic weak D
C trans
Partial D
mechanism where D antigen appears to be complete but fewer in numbers
Genetic Weak D
mechanism where there is position effect due to interaction of the gene
C trans
mechanism where there is one or more of D epitopes within the protein missing/altered; weaker agglutination w/ D reagent
Partial D (D Mosaic)
why is antibody production not stimulated by weak D phenotype
Because Rh D protein changes occur inside the red cell and is not exposed
how can weak expression be detected
Indirect Coomb’s Test
how does Indirect Coomb’s Test work
red cells will be synthesized in vitro, and then bridged with Coomb’s reagent
what is Coomb’s reagent composed of
Anti-Human Globulin
color of Anti-Human Globulin solution
green
color indicator
Janus green
is weak D recipient and donor, respectively considered Rh positive or negative?
Rh negative for recipient
Rh positive for donor
T or F:
weak D test is required for recipients
F
what reagents should be dropped in px labeled tube
1 drop of anti-D and 1 drop of RCS
what reagents should be dropped in negative control tube
1 drop of 22% Bovine Serum Albumin, then 1 drop of RCS
what reagents should be dropped in positive control tube
1 drop of anti-D, then 1 drop of known D-Positive RCS
how to incubate the 3 tubes
in a water bath at 37C for 15 mins
after incubation, px tube shows no agglutination, what is the next step
1) wash cells 3 times with NSS and decant
2) add 2 drops of AHG rgt to all tubes and mix gently
3) cover w/ parafilm, spin for 15 secs
4) dislodge, grade
after incubation px tube shows agglutination, what is the next step
record as Rh positive
T or F:
before recording the results, you can place the tube in the rack to avoid spills
F
NEVER place the tube back in the rack before recording of results
shaking the tube too hard can cause what discrepancy
false-negative results (fragile agglutinates)
inadequate mixing of tube can cause what discrepancy
false-positive
reaction of less than 3-4+ in the D or reverse typing tubes can be caused by
shaking tube too hard, leading to false negative
grading serological reactions in tube testing:
4+
one solid agglutinate, no free cells
grading serological reactions in tube testing:
3+
several large agglutinates, clear background
grading serological reactions in tube testing:
2+
medium sized agglutinates, clear background
grading serological reactions in tube testing:
1+
small agglutinates, turbid reddish background
grading serological reactions in tube testing:
1+w
very small agglutination, turbid background
grading serological reactions in tube testing:
W+ or +/-
barely visible agglutination, turbid background
grading serological reactions in tube testing:
MF
mixed field, mixture of agglutinated and unagglutinated red cells
grading serological reactions in tube testing:
H
complete hemolysis, grossly red supernate, no rbcs present
grading serological reactions in tube testing:
PH
partial hemolysis, red supernate but some rbcs remain
once the reaction is negative, proceed with what test
check cells
how many drops of check cells are added
2 drops
positive check cells indicate
confirms negative result
negative check cells indicate
repeat entire procedure (invalid/improperly done)
specimen for weak-d testing
negative test from Rh typing
most important step of weak-d testing
washing
what are the check cells used in weak-d testing
“O” red cells coated w/ anti-D added to negative anti-D test
manner of reporting for (+ grading) anti-D (slide or tube)
Rh positive (+)
manner of reporting for (0 grading) anti-D (slide or tube)
Rh negative (-) (initial)
manner of reporting for (0 grading) AHG test
Du negative (-)
manner of reporting for (+ grading) AHG test
Du positive (+)
what happens when a person with Rh negative Du positive receives an ABO compatible Rh positive blood
the person might develop antibody against the missing part in the D antigen (D mosaic)
