Quiz 6 Flashcards
What do you do when an antibody screen is positive? Why?
- Antibody Identification
2a. to avoid patient hemolytic transfusion reactions
2b. to detect and monitor patients at risk of delivering infants with Hemolytic Disease of the Fetus and Newborn (HDFN)
What type of antibodies attack RBC antigens?
- Alloantibodies
- Naturally occurring antibodies
- Autoantibodies
Who is required to take an antibody screen?
- Blood Donors
- Transfusion Recipients
- Obstetric Patients (Pregnant Moms for HDFN and RHIG[Rh immune Globulin])
What is the antibody screen test tube method?
Patient’s serum or plasma is mixed with RBC’s that have known antigen content
How do you perform the antibody screen test tube method?
- Mix patient serum/plasma + RBC w/ known antigen
- Immediate spin phase
- 37C incubation
- Add enhancements (optional)
- Centrifuge and then read for hemolysis or agglutination at 37C
- Wash 3-4x
- Add AHG, centrifuge, and read at AHG
- If all are negative, add check cells
How are check cells made?
Rh+ RBCs coated w/ Anti-D antibodies
What do check cells check for?
Checks if you added Coombs serum and/or if you washed the RBCs properly
Are antibody screens direct or indirect testing? Why?
- INDIRECT
- Antibodies will not bind/coat the RBC in vivo. Only coats in vitro
Would hemolysis be considered a positive or negative reaction?
- Positive
If hemolysis is present, what do you write in?
“H”
What are screening cells?
2-3 different donors that are group O w/ at least one cell grp antigen present
Why are homologous expression preferred for RBC reagents over heterozygous (in antibody screens)?
- Homologous expression will show a stronger reaction.
- If the patient is has heterozygous expression, a heterozygous RBC reagent’s titer may be too low. There will be little to no reaction and will be misread.
What are some enhancement reagents?
22% albumin, Low Ionic Strength Solution (LISS), Polyethylene Glycol (PEG)
What does 22% albumin do?
reduces zeta potential
(due to diff. in electrical potential and reduces negative charge)
What does Low Ionic Strength Solution (LISS) do?
Lowers zeta potential and increases uptake of antibody onto the rbc (increases sensitization)
If you add Low Ionic Strength Solution (LISS) as an enhancement reagent, you have to read
MICROSCOPICALLY IF NOT VISIBLE MACROSCOPICALLY!!!!
If you add Polyethylene Glycol (PEG) as an enhancement reagent, you cannot read at ____. You must only read _____
- 37C
- MACROSCOPICALLY at AHG
What does Polyethylene Glycol (PEG) do?
reduces H2O conc., increases antibody conc.
If this C3b if converted to C3d, what happens? Why?
- RBCs are protected from hemolysis.
- Macrophages have receptors for C3b, but not C3d.
What is in polyspecific AHG?
antibodies for both IgG and Complement
What is in monospecific AHG?
antibodies for EITHER IgG OR Complement
Some rare anti-jk AB can only be detected by complement they bind to, so they can be missed by _________ IgG AHG. Monospecific or Polyspecific IgG?
monospecific
How do you do an antibody screen w/ gel methodology?
Differences: Microtubules w/ dextran acrylamide gel (anti-IgG in gel), 0.8% conc. of Screening cells in LISS
1. Add patient’s plasma/serum and 0.8% LISS Screening cells to reaction chamber above the gel
2. Incubate card at 37C for 15-60 minutes for possible antibody sensitization
3. Centrifuge the card to allow RBCs to sink into the gel
4. Agglutinated cells will have trouble sinking to the bottom (4+ at the top, 0 at the bottom)
What is an advantage of antibody screen w/ gel methodology?
- No washing
- No coombs control steps
What does a 4+ look like in antibody screen w/ gel methodology?
One big button at the top
What does 3+ look like in antibody screen w/ gel methodology?
Agglut. cells at the upper half of the gel
What does 2+ look like in antibody screen w/ gel methodology?
Agglut. cells the whole length of the gel
What does 1+ look like in antibody screen w/ gel methodology?
Agglut. cells at the lower half of the gel
What does 0+ look like in antibody screen w/ gel methodology?
all pellet at the bottom
If there is agglutination at room temp (IS), what type of AB is it? What are some examples?
- IgM antibodies
- anti-P1, anti-N, and anti-I
If there is agglutination at AHG phase, what type of AB is it?
IgG
What is a autologous control? Normally, it should be negative or positive?
- Patient RBC against Patient Serum/Plasma
- Negative
If a patient has a positive antibody screen and a negative autologous control, what is likely to be present?
alloantibody (naturally occurring antibody against foreign cells/tissues)
Note:
- check if patient has been pregnant or transfused in the past 3 months
If a patient has a positive antibody screen and a positive autologous control, what is likely to be present?
autoantibody (naturally occurring antibody against self cells/tissues)
Does a single antibody act at the same/different phase and strength?
SAME phase and strength! unless it shows dosage
Do multiple antibodies act at the same/different phase and strength?
DIFFERENT phase and strength
If there is hemolysis present at antibody screen, what can be present?***
anti-Vel, anti-Tja, and anti-H (Bombay)
If there is mix field present at antibody screen, what can be present?***
Anti-Lu(a)
When should you suspect rouleaux?
any patient plasma/serum tests that have a reaction
what do you do if rouleaux is present? (solving)
saline replacement technique
At what phases do you read an antibody identification panel?
IS, 37C, AHG
What is important to know about the patient when reading an antibody identification panel?
Age, Sex, Race, Medications/Health Conditions, Pregnancy/Transfusion History, etc.
What are some possibilities of DAT/autocontrol being positive?
- Autoimmune disorder
- Medication
- Pregnancy
- Transfusions
If someone who had a transfusion/pregnancy, in the last 3 months, has a positive DAT/autocontrol result… why is it possibly dangerous?
may have a delayed hemolytic transfusion reaction due to alloantibody (natural AB against foreign body
What ABO group are screening cells?
grp O
What do you rule out in antibody identification panels?
- RBCs with all Negative RBC Reaction
- (all neg.) cross out homozygous expression (ex. 0,+)
How do you evaluate panel results?
- What phase(s) and strenth(s) did the +ive reactions occur? If different there can be,
1a. More than 1 antibody
1b. 1 antibody showing dosage
1c. Antigen w/ variable expression
T or F, Strength of reaction DOES demonstrate antibody significance.
False, strength does not mean anything for AB significance
If a single __-antibody is present in an antibody id panel, it matches a pattern of antigen expression exactly
allo(antibody)
When would you use select cell panels?
- when you have ruled out all common antibodies
- when you have a known antigen and you want to see if there are any additional unknown antigens
What if every cell panel reacts with a…
1. Positive Autocontrol?
2. Negative Autocontrol?
3. just they all react..
- Pregnant/Transfusion (mixed field)
- Alloantibodies against high prevalence antigens (equal strength!)
- Multiple alloantibodies
When would you do an autoadsorption/alloabsorption (remove autoantibody/alloantibody)?
If there are 2 alloantibodies present and one is stronger than the other.
Basically one has a stronger reaction than the other alloantibody, so you have to remove the stronger one to be able to see the 2nd alloantibody
What do you need as evidence to prove a suspected antibody? (95% probability)
- Three antigen POSITIVE cells w/ agglut.
- Three antigen NEGATIVE cells showing no reaction
