Blood Bank Clinical Study Questions Flashcards
What immunoglobulin class is primarily associated with the antibodies of the ABO system?
IgM
What is weak-D (Du)?
Occasionally, an individual will have significantly decreased amounts of the D antigen, and therefore will not test positive at immediate spin but will show positive on an IAT.
Why are controls used in weak-D testing, and what is done if the control is positive?
Controls are used to confirm that all reagents are working properly, since weak-D will not show up on immediate spin like full expression of D will. If the control is positive, the test is invalidated and must be repeated.
What Rh type blood products would be given to a person who was weak-D positive?
Rh=. **Blood from a weak-D positive donor is always considered Rh+. However, some weak-D positive patients can actually have a partial or mosaic form of D, and receiving Rh+ blood could still cause them to produce anti-D.
From what plant does the anti-H lectin come from?
Ulex europaeus
What effect does time have on agglutination reactions?
antibodies and antigens must be given an appropriate amount of time to react with one another; too little time can lead to a false =, while too much time can lead to a false +
What effect does temperature have on agglutination reactions?
depending on the type of antibody (ex. cold or warm auto), temperature can affect whether or not the anitbody reacts
What effect does centrifugation have on agglutination reactions?
enhances the reactivity by forcing the antigens and antibodies closer to one another
Which blood group system is the only system in which the antibodies are consistently and predictably present in the serum of normal individuals whose red blood cells lack the antigen?
ABO
What are the eight important subgroups of A?
A1, Aint, A2, A3, Am, Ax, Ael, Ay
What type of problems can subgroups of A cause in the laboratory?
they can cause discrepancies in the ABO typing process
What antibody is commonly found in some subgroups of A that can cause ABO discrepancies?
anti-A1
Mixed-field agglutination in ABO grouping would most likely be caused by what group?
A3
What is the H substance?
the precursor of the A and B antigen, formed by the addition of fucose to the terminal galactose on either Type I or II chains.
What is the minimal acceptable weight for donating blood?
> /= 110lbs (50kg)
What is the acceptable temperature for donating blood?
= 37.5C (99.5F)
What is the acceptable range for pulse when donating blood?
50-100 bpm
What is the acceptable blood pressure for donating blood?
systolic:
What is the acceptable hemoglobin level for donating blood?
> /= 12.5 g/dL
What is the acceptable hematocrit level for donating blood?
> /= 38%
What is Landsteiner’s Rule?
antibodies are present in plasma only when the corresponding antigen is not present on the red blood cells
What is the principle of the copper sulfate method for determining hemoglobin based on?
Copper sulfate has the same specific gravity of blood with a hemoglobin measurement of 12.5 g/dL, the minimum for blood donation. If a drop of blood placed into a copper sulfate solution is maintained within 12 seconds, hemoglobin is adequate. If the drop sinks, the hemoglobin is higher than 12.5; if it floats, the hemoglobin is lower than 12.5.
What is the specific gravity of copper sulfate?
1.053
What is an autologous transfusion?
any transfusion of blood or blood components that have originated with the recipient
What is therapeutic phlebotomy?
the removal of blood for medical reasons
What is plasmapheresis?
the withdrawal of blood from a donor and subsequent return of red blood cells
What are packed red cells?
blood from which plasma has been removed
What does leukoreduced mean?
at least 70% of the original white blood cells have been removed but at least 70% of the original red blood cells have been retained
What is cryoprecipitate?
the cold insoluble portion of plasma remaining after FFP has been thawed
What are frozen-stored red blood cells?
prepared by freezing red blood cells using glycerol as the cryoprotective agent
What is the criteria for the age of compatibility testing specimens?
For patients who have, in the last three months, been pregnant or have received a transfusion (or if the history is uncertain or unavailable), the sample used for compatibility testing must be obtained from the patient within three days of the scheduled transfusion; this represents the patient’s current immunological status, and complement is present in fresh plasma only. **There’s not set time limit on crossmatch specimens for patients who do not meet this criteria, though some hospitals set the three-day limit for all specimens to avoid problems.
What is the most current preservative used for blood storage?
CPDA (citrate-phosphate-dextrose-adenine)
What is the shelf life of CPDA-stored blood?
35 days @ 1-6*C
Define allele.
one of two or more different genes that may occupy a specific locus on a chromosome
Define phenotype.
the outward expression of genes; on blood cells, the serologically demonstrable antigens constitute the phenotype, except those sugar sites that are determined by transferases
Define locus.
the site of a gene on a chromosome
Define silent allele.
a gene that does not appear to produce a detectable antigen
Define heterozygous.
possessing two different alleles at a given gene locus
Define Rouleaux, including causes.
“stacked coin” appearance of RBCs; may be artifactual (as on thick blood smears) or caused by abnormal proteins, increased fibrinogen, and increased globulins, such as in infection and inflammation, and disease states (multiple myeloma, Waldenstrom’s, cirrhosis, etc.)
Define amorph.
another name for “silent allele”
Define alloimmunization/isoimmunization.
development of antibodies in response to alloantigens (derived from a genetically dissimilar animal of the same species) such as following a transfusion
Define LISS.
Low Ionic Strength Solution; enhances agglutination reactions by reducing the zeta potential and increasing the amount of antibody taken up by the RBCs
Define Bombay phenotype, including all antibodies present in the serum.
hh, Oh; RBCs do not express the H antigen, and therefore cannot express the A or B antigens, no matter what their genotype. Serum contains anti-A, anti-B, and anti-H, so Bombay individuals can only receive blood products from other Bombay individuals.
Define compatible.
donor red cells that do not contain the antigens that correspond to antibodies present in the recipient serum
Define homozygous.
possessing a pair of identical alleles at a given gene locus
Define kernicterus.
also known as bilirubin encephalopathy; a disorder causing severe jaundice in newborns, wherein bilirubin is deposited in the brain, potentially leading to athetoid cerebral palsy, hearing/vision problems, or mental retardation
Define incomplete/blocking antibody, including antibody class.
IgG class; antibodies that do not cause agglutination when suspended in saline, however they do block the antigenic sites on RBCs so that subsequent addition of complete antibody of the same antigenic specificity does not cause agglutination.
Define Wharton’s jelly.
Gelatinous substance within the umbilical cord, largely made up of mucopolysaccharides, derived from extra-embryonic mesoderm. To remove it, RBCs must go through several wash cycles with isotonic saline.
Define genotype.
an individual’s actual genetic makeup
Define homologous antigen and antibody.
the specific antigen that generates the formation of an antibody that in turn can react with that antigen
Define adsorption.
the uptake of antibody by the target antigen
Define forward typing.
patient red cells are combined with A, B, and D antisera, centrifuged, and observed for agglutination, which determines blood type and Rh status
Define reverse typing.
patient plasma is combined with A1 and B reagent red cells, centrifuged, and observed for agglutination; results should be the opposite of the forward typing
Define polyagglutination.
red cells that are agglutinated by almost all samples of human sera from adults, but not by autologous serum or the sera of newborns; can be transient or persistent
Define dosage effect, including an example.
phenomenon in which red cells from homozygous people possess more antigens per red cell than do cells from heterozygous people; the effect is exhibited by the corresponding antibodies reacting more strongly with cells from homozygous people (anti-e is an example)
Define crossmatch.
testing the compatibility of a donor’s red cells with recipient serum
Define secretor, including percentage of population.
a person who secretes their blood type antigens into body fluids and secretions such as saliva, digestive tract/respiratory tract mucus, etc.; ~80% of the population are secretors
Define antibody titration.
measurement of how much antibody an organism has produced that recognizes a particular epitope, expressed as the inverse of the greatest dilution that still gives a positive result
Define zeta potential.
measure of the magnitude of the electrostatic or charge repulsion/attraction between particles
Define Rhnull.
individuals whose red cells have no Rh antigen on their surfaces
Define saline replacement technique.
Technique used to resolve discrepancies in Rh or ABO reverse typing. For Rh, cells are washed with saline and retested with anti-D. For ABO reverse, cells are spun down and the plasma is replaced with an equal volume of saline to rule out Rouleaux.
Give two situations in which a FMH screen is done.
at delivery (Rh= mother, no history of alloanti-D, cord blood Rh+); pregnant mother has suffered some sort of trauma, such as a car accident
Name five sources of error that may lead to a false = result in an antiglobulin test.
incubation time and/or temperature is incorrect; patient plasma accidentally left out of testing; panel cell suspension is too light; improper centrifugation; improper storage of materials
Name five sources of error that may lead to a false + result in an antiglobulin test.
antibody in patient plasma to antibiotics and/or components of preservative; microbial contamination; panel cell suspension too heavy; improper centrifugation; improper storage of materials
What is D+w?
weak expression of the D antigen (can also be written as Du)
How is weak D detected?
Indirect Antiglobulin Test (IAT); patient serum is incubated with reagent screening cells and observed for agglutination (if agglutination is seen, full antibody ID panel must be performed)
What are the two lectins used in routine blood banking, and what are their sources?
anti-A1 lectin, derived from the Dolichos biflorus plant; anti-H lectin, derived from the Ulex europaeus plant
How are anti-A1 and anti-H lectins used?
anti-A1 distinguishes between the A1 and A2 subgroups, which can help to resolve ABO typing discrepancies; anti-H is used in secretor testing, as all secretors will test positive with anti-H regardless of their blood type
What are four causes of ABO discrepancies?
weak antigen expression, cold reactive antibodies, subgroups of A, strongly reactive cold autoagglutinins
What is the role of a weak-D positive individual as a donor?
weak-D positive blood is considered to be Rh positive
What is the role of a weak-D positive individual as a recipient of blood products?
weak-D positive patients should receive Rh negative blood products; these patients could in fact be D-mosaic, and there is a chance that Rh positive blood could elicit a form of anti-D
What is the theory behind the Fisher-Race system?
it assumes that three closely linked genes are inherited from each parent, each one coding for a specific antigen that can be detected (Cc, Ee, D)
What is the theory behind the Wiener system?
it assumes that only one Rh gene is inherited from each parent
Compare the notation of the Fisher-Race system to the Wiener system.
Dce (Rzero), DCe (R1), DcE (R2), DCE (Rz), dce (r), dCe (r’), dcE (r”), dCE (ry)
Explain the difference between the DAT and the IAT.
the DAT determines whether red cells have been coated in vivo (in the body) with immunoglobulin, complement, or both; the IAT determines whether there is antibody in the serum or plasma (considered an in vitro test)
Name four conditions that exhibit a positive DAT.
hemolytic transfusion reaction; HDFN; cold autoantibodies; paroxysmal cold hemoglobinuria (PCH)
What three procedures in the blood bank incorporate the IAT?
antibody screening; crossmatching; antigen typing
How can the antibody be identified that causes red cells to be DAT positive?
if the initial screen with polyspecific sera is positive, testing with monospecific sera can determine if it is IgG, C3b, or C3d; if it is IgG, an antibody panel can determine the identity
What kind of incompatibilities and antibodies does the saline or immediate spin phase detect?
ABO
LISS can be used to enhance direct agglutination of red cells by antibodies of what class?
IgG
What phase is required when testing samples from recipients for the presence of clinically significant antibodies and for serologic compatibility with donor red cells in some cases?
immediate spin
What class of antibody usually reacts at immediate spin and which systems do they belong to?
IgM; M, Rh, N, Lewis, and P1
What class of antibody usually reacts in the AHG phase and which systems do they belong to?
IgG; Kell, Kidd, and Duffy
What is the principle of the Kleihauer-Betke test?
fetal hemoglobin (Hgb F) is resistant to acid elution, whereas adult hemoglobin is not; therefore, in the event of a FMH, if the blood smear is immersed in acid buffer, adult hemoglobin will be eluted from the red cells and the Hgb F will remain
What is unusual about the Xg blood group system?
the Xga antigen’s presence is determined by a gene on the X-chromosome, making it more common in females than in males
The latest technology is “tubeless”, which utilizes what to perform ABO grouping, Rh typing, and antibody detection?
gel cards
What are the naturally occurring antibodies, possible genotypes, and phenotypes of the A blood group?
anti-B; A1A1, A1A2, A1O (all phenotype A1); A2A2, A2O (both phenotype A2)
What are the naturally occurring antibodies, possible genotypes, and phenotypes of the B blood group?
anti-A; BB, BO (phenotype B)
What are the naturally occurring antibodies, possible genotypes, and phenotypes of the AB blood group?
no antibodies; A1B, A2B (phenotypes are the same as the genotypes)
What are the naturally occurring antibodies, possible genotypes, and phenotypes of the O blood group?
anti-A, anti-B, anti-A,B; OO (phenotype O)
If a mother with genotype BO and a father with genotype AO have a child, what are the possible genotypes for the child?
AB, AO, BO, OO
At what temperature should blood bank blood be stored?
2-8*C
How would you differentiate between A1 and A2?
test cells with anti-A1 lectin; A1 cells will agglutinate, A2 cells will not
What is the common name for erythroblastosis fetalis?
hemolytic disease of the fetus and newborn (HDFN)
Discuss the pathogenesis of HDFN.
The fetus inherits a blood group from its father that is foreign to the mother. Fetal red cells cross the placenta and enter the maternal circulation during pregnancy, and especially at delivery. Typically, the volume of red cells before delivery is too small to induce primary sensitization; rarely does a mother produce detectable antibody during the first pregnancy. However, if the mother produces IgG alloantobodies on these cells, fetal red cells will be destroyed in subsequent pregnancies. Antibody originating in the maternal serum enters the fetal circulation through the placenta, attaches to blood group antigen on the fetal red cells, and causes cell destruction. To compensate for the resultant anemia, the fetal bone marrow responds excessively; other sites of red cell production (spleen, liver, kidney) may also be brought into use. Jaundice, anemia, and enlargement of the liver and spleen are clinical signs of HDFN. HDFN can cause mild anemia, mental retardation, brain damage, and even death depending on the severity. Heart failure due to extreme anemia is thought to be the major cause of intrauterine death. Hydrops fetalis (generalized anemia) can occur, as well as kernicterus, an infiltration of the brain and spinal cord with unconjugated bilirubin which causes permanent damage to the CNS. Fetuses that survive gestation can be saved by exchange transfusion shortly after delivery.
When is the MN group of great importance?
if M is whole or partially IgG, it becomes clinically significant
What is Coomb’s reagent?
serum from rabbits, or other animals, previously immunized with purified human globulin to prepare antibodies directed against IgG and complement
Name the two different types of Coomb’s reagent and describe them.
polyspecific - contains antibodies to IgG, C3b, and C3d; monospecific - contains antibodies to only one of the components in polyspecific
Why are the red cells used in an antiglobulin test washed?
to remove any residual unbound IgG, unbound proteins, or to remove Wharton’s jelly (cord samples) that may interfere with testing
List the selection of donor units in order of preference for each blood group.
O - O blood only; A - A, O; B - B, O; AB - AB, A or B, O
What is the most common type of transfusion reaction?
non-hemolytic febrile reacton
How does an injection of RhoGam (RhIG) prevent Rh sensitization?
RhIG is thought to work, in part, by inhibition of the normal antibody-mediated immune response that creates anti-D antibody. Administration of anti-D antibody in RhIG coats any fetal cells, disallowing production of active maternal anti-D antibody.
Who are candidates for RhoGam?
Rh negative women as an antenatal dose at approximately 28 weeks or at any time during pregnancy; Rh negative women who have delivered a baby that is Rh positive, Rh unknown, or Rh invalid; Rh negative women who have suspected exposure to fetal cells such as in cases of fetomaternal hemorrhage, trauma, miscarriage, cordocentesis, or amniocentesis; Rh negative patients who have received blood products which may contain Rh positive cells
In the case of pregnant females, when is RhoGam administered?
at approximately 28 weeks and/or at delivery
What are the donor blood characteristics required for an exchange transfusion for the treatment of HDFN.
blood products must be compatible with both the baby and the mother; must be CMV and Hgb S negative; plasma must be FFP only, DO NOT use cryoprecipitate
Within what time frame must a unit of blood be transfused once the hermetic seal has been broken?
within 4 hours if kept at room temperature, and within 24 hours if refrigerated at 1-6*C
What results might lead a tech to suspect that two or more antibodies are causing an incompatibility?
all cells on the screen are positive; mixed field reaction; varying reaction degrees from cell to cell; reactions at more than one phase in tube testing
What is antibody screening?
testing a patient’s plasma against screening cells with known antigens to determine whether or not potentially clinically significant antibodies are present in the plasma
Is an antibody screen part of a crossmatch?
yes
What is an elution?
dissociating antibodies that are attached to the surface of red cells
Why are elutions performed?
aids in the diagnosis of AIHA; diagnosis of ABO HDFN; identification of specificity when multiple antibodies exist in a patient’s plasma or serum; phenotyping red cells in patients with a positive DAT
Name two elution techniques, including which antibodies they best detect.
Lui Freeze-Thaw Elution (ABO antibodies); acid elution (resolution of multiple antibodies)
What does a positive DAT on a cord blood sample mean?
an indication of HDFN caused by ABO incompatibility or by maternal IgG antibody crossing the placenta
When may Rh typing of a newborn give false negative results?
when the baby is weak-D positive
When may Rh typing of a newborn give false positive results?
HDFN due to anti-D
What tests on newborns would alert you to the possibility of false Rh results?
all newborns with an initial negative for Rh are reflexed to weak-D testing (@NHRMC); a positive DAT on a cord sample will alert for possible HDFN
How would an infant’s true blood type be determined in the case of false Rh results?
false = would be weak-D tested (incubated for 15 minutes, washed, and tested with anti-IgG); false + would have a type and screen performed on a cord blood sample
What is the main prenatal risk due to HDFN?
anemia, hyperbilirubinemia, jaundice
What is the main postnatal hazard due to HDFN?
kernicterus
What must be done in the event of an emergency release of blood products?
- Obtain a patient sample for crossmatch regardless of when the crossmatch can be performed; 2. Record the patient’s name and MR#; 3. If there is time for a type and screen, perform one and issue ABO compatible blood. If there is not time, issue O= blood products and switch to ABO compatible once the type and screen has been completed; 4. Stamp each transfusion record with a red ink stamp notifying that the compatibility testing has not been completed; 5. Complete an authorization form for emergency release and send with the issued blood products - the attending physician MUST sign this form; 6. Notify the physician and/or the nurse when compatible blood is available; if an antibody has been detected; or if the emergency release products were found to be incompatible. If the patient has received incompatible units, notify the medical director or the pathologist on call IMMEDIATELY and complete a blood product deviation form.
Describe the action of enzymes on red cells.
enzymes can either enhance or diminish the reactivity of certain antibodies and red cell antigens
What four enzymes are utilized in blood banking?
ficin, trypsin, papain, and bromelain
What antibodies are diminished by enzymes?
MN, Duffy, and Xga
What antibodies are enhanced by enzymes?
ABORh, P, Lewis, and Kidd
How does the Lewis blood group system differ from the other systems?
believed to be the only system that is not manufactured by the red cells; instead, antigens are manufactured by the tissue cells and secreted into body fluids, where they are absorbed onto the red cell membranes (they are not an intrinsic part of the membranes)
What is the total amount of blood routinely taken from a blood donor?
450 mL +/- 10%
