Blood Bank
Kernicterus
Accumulation of unconjugated biliruin in the brain.
A Kleihauer-Betke test reveals 0.5% fetal cells are present in maternal circulation. Assuming a maternal blood volume of 5000 mL, what is the appropriate dose of RhIG to give this patient? (Please show your work)
5000 mL x .005 = 25 mL 25 mL / 30 = 0.83 vials = 1 vial RhIG add 1 vial for overkill = 2 vials
A Direct Antiglobulin Test (DAT) is positive with both polyspecific and monospecific anti-IgG AHG reagents. To validate these results, one should test the RBCs against:
6% BSA control
A rise in antibody titer of_____or more tubes is considered significant
2
A 300 ug dose of RhIG is sufficient to protect against ____ mL of fetal whole blood.
30
Erythroblastosis fetalis
Release of erythroblasts into fetal circulation due to severe anemia
How does ZZAP affect the RBC membrane?
The dithiothreitol (DTT) in ZZAP breaks down the IgG monomers coating the RBC. The papain enhances expression of Kidd, Lewis, Rh, Ii, P1 and ABO antigens while destroying MNSs, Duffy and Xga
An MLS has performed DATs on several patients, all of whom had 2+ reactions with the AHG reagent and with the BSA control. The MLS is now seeing similar reactivity in all of his antibody screens. What might be causing these results?
The most probable cause of a scenario such as this is contaminated saline. Switch to a different source of saline for washing cells at the AHG phase; the problem should be resolved.
Why is a clot tube not used for the DAT?
The serum in the clot tube still contains complement which can be activated during storage, in which case it is no longer a measure of what is happening in the patient's body.
What makes it possible for IgG antibodies to cross the placenta?
There are receptors on the placenta for the Fc portion of IgG.
What is the purpose of testing the last wash?
There should be no free antibodies in the last wash. The last wash serves as a negative control.
What is the principle of the acid elution method?
Washed RBCs are suspended in a glycine solution at pH 3.0 to dissociate bound antibodies from the RBC membrane (RBC antigens destroyed). The supernatant (eluate containing antibodies) is neutralized by a buffering solution, and then tested against known RBC antigens in order to identify the antibody specificity.
Which elution method uses papain and DTT to alter the RBC membrane?
ZZAP
When is an elution performed?
• When the DAT is positive due to IgG, in order to identify the antibody coating the RBCs. • To remove antibodies coating the RBCs in order to use the RBCs in an adsorption procedure or to antigen type the RBCs.
What is the most common error made when performing the DAT?
Improper washing of cells before testing (false negative results)
Which is the first specimen of choice when crossmatching blood for an exchange transfusion?
Mother's serum has a higher antibody titer than the infant's serum, will be more plentiful, and can be obtained in advance of delivery. Infant's serum and an eluate prepared from the infant's RBCs are both good second choices when mother's serum is not available. Father's serum is not useful, as he does not have the antibody that is causing HDFN in the infant.
Rh immune globulin is given to Rh ____ mothers who have given birth to Rh ______ babies within _____ hours of delivery. The mother must not already have ______ anti-D in her serum.
Negative, Positive, 72, immune
Rh HDFN can occur if the mother is Rh ________ and the infant is Rh_____.
Negative/Positive; Mother must lack the D antigen in order to make anti-D. The infant must possess the D antigen in order for the maternal anti-D to sensitize the infant's RBCs.
Responsible for causing HDFN? Ii
No risk of HDFN
Responsible for causing HDFN? P1
No risk of HDFN
The last wash (LW) is tested in parallel with an eluate to prove:
No unbound antibody remains in solution
ABO HDFN can occur in infants born to Group _____mothers
O; Group O individuals have IgG forms of anti-AB, anti-A and anti-B
An Rh Negative woman received RhIG as part of her routine prenatal care at 26 weeks gestation. When she went into labor at 38 weeks, a Type and Screen was weakly positive with screen cells I and II at the AHG phase of testing, but was negative with screen cell III. What is the most likely explanation for these results?
Patient has residual anti-D from antenatal RhIG
ABO HDFN and mild cases of bilirubinemia can usually be treated by _____.
Phototherapy
Rationale for intrauterine exchange criteria: Irradiation
Prevent Graft vs. Host Disease
Rationale for intrauterine exchange criteria: Hgb S Neg
Prevent RBC sickling in hypoxic recipient
Rationale for intrauterine exchange criteria: CMV Negative
Prevent potentially fatal viral infection
Extramedullary hematopoiesis
Production of blood cells outside of the marrow. Leads to enlarged liver and spleen.
DAT or IAT? Investigates in vitro sensitization of RBCs
IAT only
DAT or IAT? Requires a 37C incubation step to achieve cell sensitization
IAT only
DAT or IAT? Uses either patient's RBCs or plasma
IAT only
RhIG is used to prevent HDFN due to _________.
Anti-D only
Name 3 Blood Bank tests that should be performed on every obstetrical (OB) patient's prenatal specimen early in pregnancy that allows the physician to assess the risk of HDFN to the fetus.
ABO, Rh, antibody screen
If the patient has a positive DAT, which tests may be falsely positive?
Antigen typing that is read at the AHG phase, weak D test, Antiglobulin crossmatch, D determination using high protein anti-D typing sera
A Medical Laboratory Scientist (MLS) is performing a DAT. After the washes are complete, but before the AHG reagent is added, the MLS is interrupted with a phone call requesting blood on another patient STAT! After filling the STAT request, the MLS returns to the DAT, adding the AHG reagent. The results of the DAT are negative. However the Check Cells fail to react. What are possible causes for the Check Cells results?
Assuming the MLS really did add the AHG reagent (one cause of a false negative is forgetting to add reagent!), one possibility is the gap in time between washes and adding the AHG. IgG may dissociate from the RBC surface, leaving too little IgG on the RBC to effectively react with the antiIgG. The now free IgG may neutralize the anti-IgG in the reagent, also causing a false negative result. Other possible causes include improper washing of RBCs before testing, improper cell suspension concentration, neutralization of AHG reagent, saline not at a neutral pH, and undercentrifugation.
Hydrops fetalis
Cardiac failure with generalized edema
Responsible for causing HDFN? Duffy
Causes HDFN
Responsible for causing HDFN? Kell
Causes HDFN
Responsible for causing HDFN? Kidd
Causes HDFN
Responsible for causing HDFN? Rh
Causes HDFN
Which of the following partial elution methods weakens Rh antigens?
Chloroquine
Name a chemical that can be used to partially elute antibodies from an RBC in order to antigen type the RBC?
Chloroquine diphosphate or EGA
Rationale for intrauterine exchange criteria: O Rh Negative
Compatible with infant's RBCs
Rationale for intrauterine exchange criteria: Antigen negative
Compatible with mother's antibody
A technologist inadvertently used a clotted sample that had been refrigerated overnight to perform a DAT. An erroneous result may occur because:
Complement may be activated in vitro.
DAT or IAT? investigates in vivo sensitization of RBCs
DAT
DAT or IAT? Uses IgG sensitized cells to confirm negative reactions (Check cells)
DAT and IAT
DAT or IAT? Washing step to remove unbound globulins from test environment
DAT and IAT
DAT or IAT? Useful in detecting drug induced hemolytic anemia
DAT only
The definitive test performed on the infant for diagnosis of HDFN is the:
DAT; For HDFN to be diagnosed there must be evidence that maternal antibodies are destroying the infant's RBCs. The DAT will provide this evidence
The greatest danger for the fetus affected by HDFN prior to birth is:
Death due to anemia
In suspected HDFN, what significant information can be obtained from a peripheral blood smear?
Determination of the presence of spherocytes and elevated numbers of NRBCs; Spherocytes are a sign of hemolysis, and are commonly present in ABO HDFN (rare in Rh HDFN). Nucleated RBCs are a sign of increased erythropoiesis.
Which elution method relies on lowering the pH to 3.0 in order to dissociate antibody from the RBC membrane?
Elu-Kit
The process of removing antibody from red blood cell membranes is called
Elution
True or False: If a pregnant woman has anti-E, and the baby's father is R1R1, the baby may be affected by HDFN.
False; The baby's father is DCe/DCe, so there is no chance that the baby's RBCs will possess the E antigen.
________________ is a screening test for fetomaternal bleeding. The ______________ test can quantitate the amount of fetomaternal bleeding.
Fetal Maternal Hemorrhage Screen / Kleihauer-Betke
Name one clinical condition in which a person would have a positive DAT due to alloantibodies directed against RBC antigens.
HTR & HDFN
Why are high bilirubin levels a greater concern in a baby after it is born than in utero?
In utero, the infant's bilirubin crosses the placenta, and is conjugated by the mother's liver. The mother then excretes it. After delivery, the infant's liver must conjugate the bilirubin without assistance
The most common error made when performing the DAT by tube method is:
Inadequate washing of RBCs
What is the principle of the antiglobulin test?
Sensitized RBCs are agglutinated when the Fab of the antibodies in the AHG reagent bind to the Fc portion of antibodies or to complement bound to the RBC surface.
Blood for an exchange transfusion must be compatible with mother's _____ and baby's _______.
Serum/ red blood cells
What is the basic principle of the Kleihauer-Betke test?
Solubility of adult hemoglobin in an acid solution
Rationale for intrauterine exchange criteria: Fresh
Supply high levels of 2,3-DPG and low plasma K+
The main difference between the DAT and an IAT is:
The DAT tests for RBCs that were sensitized in the body while the IAT allows sensitization to occur during the incubation phase.
