blood bank physiology and pathophysiology part 3
Which symptom of hemolytic disease of the fetus and newborn (HDFN) is associated with low levels of glucuronyl transferase? The correct answer is highlighted below Anemia Increased reticulocyte count Jaundice Cardiac failure
In HDFN, anemia generally occurs in utero as maternal IgG antibodies cross the placenta and bind to the corresponding fetal antigen. Red cell destruction is caused by macrophages in the fetal liver and spleen. The fetus attempts to compensate for anemia with increased erythropoiesis in the liver and the spleen, causing an increased reticulocyte count as immature red cells enter the circulation. Jaundice in a newborn suffering from HDFN is associated with low levels of glucuronyl transferase, a liver enzyme that conjugates bilirubin into its water-soluble, excretable form. Cardiac failure may occur because of untreated, uncompensated anemia.
Severe blood loss causing circulatory collapse and shock usually first occurs when what percentage of blood is lost? The correct answer is highlighted below 5 to 10% 20% 30 to 40% 60%
According to McKenzie and Williams (2015), severe blood loss of 30 to 40% of total blood volume leads to circulatory collapse and shock. Acute blood loss of 20% or less, in many cases, doesn't cause clinical symptoms at rest. Because of this 5 to 10% and 20% are not the correct answers. Acute blood loss of 50% or more is not compatible with life, therefore, 60% is not the correct answer. When blood is lost over a longer period of time, the body can develop compensatory mechanisms to accommodate for the loss. Because of this, circulatory collapse and shock may not develop when 30 to 40% of blood is lost over an extended period of time.
In the Kleihauer-Betke test, a maternal blood smear is treated with acid and then stained with counterstain. The fetal cells contain fetal hemoglobin, which is resistant to acid and will remain pink. Since the calculated volume of fetomaternal hemorrhage is an estimate, how many additional RhIg vials need to be added for the dose? The correct answer is highlighted below 1 1.5 2 3
After 2000 cells are counted, the percentage of fetal cells is determined, and the volume of fetal hemorrhage is calculated by the formula: number of fetal cells X maternal blood volume / number of maternal cells = volume of fetomaternal hemorrhage. Because the Kleihauer-Betke is an estimate, one vial is added to the calculated answer.
A spectrophotometric scan of amniotic fluid may be valuable in the determination of which of the following conditions: The correct answer is highlighted below Neural tube defects Maternal hypertension Hemolytic disease of the newborn Maternal diabetes
Amniotic fluid bilirubin is elevated in hemolytic disease of the newborn. It is determined by using the absorbance spectrum of amniotic fluid to determine the increase in absorbance at 450nm, which is the absorbance peak for bilirubin. This value, along with the gestational age, are used in Liley's three zone chart to determine the risk of severe fetal hemolysis.
Which antibody identified in prenatal specimens is never a cause of hemolytic disease of the fetus and newborn? The correct answer is highlighted below Anti-D Anti-c Anti-E Anti-I
Anti-I is a common autoantibody that can be found in virtually all sera. It is benign (not associated with in vivo red blood cell destruction). It is usually a weak, naturally occurring, saline-reactive IgM agglutinin. Rh antibodies are primarily IgG and Rh antigens are well developed early in fetal life. While the D antigen is the most immunogenic, c antigen is the next most likely Rh antigen to elicit an immune response, followed by E, C, and e. Rh antibodies formed by the Rh negative pregnant women coat the fetal red blood cells that carry the corresponding antigens. The coated fetal cells are removed from the fetal circulation (hemolytic disease of the fetus and newborn).
Which of the following is NOT considered a characteristic of paroxysmal cold hemoglobinuria (PCH)? The correct answer is highlighted below Patient population: children and young adults Pathogenesis: following viral infection Site of hemolysis: intravascular Autoantibody class: IgM
Characteristics or factors associated with PCH include: autoantibody class = IgG patient population = children and young adults pathogenesis = following viral infection site of hemolysis = intravascular
Fresh frozen plasma should be used for which of the following? The correct answer is highlighted below Platelet replacement Coagulation deficiencies Volume replacement Albumin replacement
FFP, or fresh frozen plasma, should be used to treat coagulation deficiencies, although the levels of factors V and VIII are usually decreased in FFP units. FFP is not used for platelet replacement as there are virtually no platelets in FFP units. FFP should never be used as a volume expander unless traumatic bleeding is taking place. Finally, FFP is not used to replace albumin in recipients.
What would be the best way to determine how much RhIg should be given to a postpartum female who received RhIG antenatally and demonstrates the anti-D antibody at delivery? The correct answer is highlighted below Antibody titration Flow cytometry Rosette test Kleihauer-Betke acid elution
Flow cytometry is able to objectively identify the number of fetal red cells in whole blood so that the number of vials to be given can be accurately calculated. Antibody titration cannot differentiate between passive anti-D or active anti-D, so it is not good practice in this situation since the patient will only benefit from RhIg if she has a passive anti-D. The rosette test is able to identify, but not quantify, D+ cells. Because of this, it cannot be used to determine the number of RhIg vials that should be administered. The Kleihauer-Betke acid elution is able to differentiate and quantify fetal and maternal red cells, but the test is highly subjective.
Which finding best distinguishes immune hemolytic anemia from other hemolytic anemias? The correct answer is highlighted below Rouleaux Positive DAT Splenomegaly Increased erythrocyte count
In the group of disorders referred to as immune hemolytic anemias, erythrocytes are destroyed too early by an immune-mediated process that results from antibodies, complement, or both attaching to the red cell membrane. The presence of immune hemolytic anemia is confirmed by a positive DAT (direct antiglobulin test). Rouleaux is the formation of red cells that are stacked and appear like a stack of coins. This is a characteristic finding in multiple myeloma. Splenomegaly, or an enlarged spleen, may be found in Gaucher's disease or in polycythemia vera. It is not found in immune hemolytic anemia. Increased erythrocyte count is not a finding in immune hemolytic anemia.
Many red blood cell (RBC) processes, such as binding, transporting, and releasing oxygen, do NOT require energy. Energy however, is required for cellular viability. How does the RBC obtain most of it's energy? Please select the single best answer Glycolytic pathways Hexose-monophosphate shunt Rapoport-Luebering pathway Methemoglobin reductase pathway
Most of the energy needed for RBC viability is obtained through the glycolytic pathway. About 90 to 95% of the cells' glucose is metabolized in this pathway, which in turn produces ATP. One glucose molecule produces a net gain of 2 moles of ATP via this pathway. The main function of the hexose-monophosphate shunt is to provide NADPH and glutathione to reduce oxidants, essentially minimizing the amount of oxyhemoglobin that would convert to methemoglobin. The Rapoport-Luebbering pathway controls the amount of 2,3-BPG that gets produced. The methemoglobin reductase pathway functions to protect hemoglobin from oxidation by NADH and methemoglobin reductase.
Antenatal Rh Immune Globulin (RhIG) is typically given at how many weeks gestation? The correct answer is highlighted below 20 24 28 32
Rh Immune Globulin (RhIG) is used to help prevent pregnant women from becoming actively immunized to the D antigen. During pregnancy and delivery, fetal blood can enter maternal circulation. This exposure to the D antigen puts the mother at risk for becoming sensitized and making an anti-D. Rh-negative women carrying an Rh-positive fetus now receive RhIG at 28 weeks (antenatal) and at delivery (within 72 hours of delivery) to clear fetal red blood cells from the maternal circulation. The RhIG can attach to fetal red blood cells, which are then cleared by macrophages. RhIG does not pose a risk to the fetus when given antenatally, but it may cause a positive antibody screen for the mother and a positive DAT for the newborn.
What kind of immunoglobulins are predominantly found in Rh immune globulin? The correct answer is highlighted below IgM anti-D IgG anti-D IgM anti-A,B IgG anti-A,B
Rh immune globulin is a solution of concentrated anti-D. It is prepared from pooled human plasma of patients who have been hyperimmunized and contains predominantly IgG anti-D. Because RhIg contains IgG anti-D, it can cross the placenta and sensitize fetal Rh positive red cells. Affected infants may be born with a weakly positive DAT, but significant hemolysis does not occur.
All of the following are indications for administering Rh immune globulin (RhIg) to an Rh negative woman, EXCEPT? The correct answer is highlighted below Therapeutic abortion Ectopic pregnancy Rh positive fetus Rh negative fetus
RhIg is not indicated for the mother if the infant is found to be D negative. The blood type of fetuses in abortions, stillbirths, and ectopic pregnancies usually cannot be determined; therefore, RhIg should be administered in these circumstances. The Rh negative (nonimmunized) mother should receive RhIg soon after delivery of an Rh positive infant.
The appropriate dosage of Rh immune globulin (RhIg) to administer post-delivery to an Rh-negative mother delivering an Rh-positive child is calculated based on the estimated volume of fetal bleed. What is the value of x in the formula given below that is used to calculate RhIg dosage? Number of vials of 300 µg RhIg = volume of fetal bleed/x mL The correct answer is highlighted below 10 30 100 300
A 300 µg vial of RhIg can prevent immunization to a fetomaternal hemorrhage (FMH) of 30 mL of D positive whole blood. Using the estimated volume of fetal bleed determined by the Kleihauer-Betke test or flow cytometry, the number of vials of RhIg (300 µg) to inject is calculated as follows: The number of vials of 300 µg RhIg = volume of fetal bleed/30 mL. In the interests of safety some American organizations recommend the following to deal with decimal points: If the number to the right of the decimal point is <5, round down and add 1 vial (e.g., 1.4 = 1 +1 = 2 vials) If the number to the right of the decimal point is greater than or equal to 5, round up and add 1 vial (e.g., 1.7 = 2 +1 = 3 vials).
A D-negative mother gives birth to a D-positive child. The result of the fetal-maternal hemorrhage (FMH) test is positive. The Kleihauer-Betke test is performed next to quantify the volume of the fetal bleed. The result of this test indicates that the mother has been exposed to 20 mL of fetal blood. How many 300 microgram vials of RhIG should the mother receive? The correct answer is highlighted below 1 vial 2 vials 3 vials RhIG is not indicated for this mother.
A single 300 microgram vial of RhIG provides protection of up to 30 mL of fetal blood. Since a 20 mL fetal bleed occurred, 0.67 vials of RhIG are needed (20mL/30mL = 0.67). Round this number up to 1 (as it is greater than or equal to 0.5) and add 1 more vial (as is the convention). Thus, 2 vials are needed. Here are a few additional examples of RhIG calculations: If 1.4 vials are calculated, round down to 1 and add 1 for a total of 2 vials of RhIG If 1.7 vials are calculated, round up to 2 and add 1 for a total of 3 vials of RhIG
If detected in antibody screen testing, which of the following antibodies is NOT considered clinically significant in prenatal patients? The correct answer is highlighted below Anti-M Anti-N Anti-Leb Anti-Fya
Anti-Leb may be detected in antibody screen testing of prenatal patients; however, this antibody is considered clinically insignificant. It is not indicated in causing hemolytic disease of the fetus and newborn (HDFN). Although rarely seen, both anti-M and anti-N can potentially cause mild to moderate HDFN. The most common clinically significant antibodies noted in prenatal patients include the following: anti-Fya, anti-K, anti-D, anti-E, anti-e, anti-C, and anti-c. These IgG antibodies have been determined to cause moderate to severe HDFN.
Who would be a candidate, at 28 weeks gestation and had a negative antibody screen, to be injected with Rh immune globulin (RhIg)? The correct answer is highlighted below Rh positive mother with Rh negative fetus Rh positive mother with Rh positive fetus Rh negative mother with Rh negative fetus Rh negative mother with Rh positive fetus
Criteria for antepartum administration include D negative mothers when the fetus is either D positive or unknown. D positive mothers are not candidates for RhIg. A D negative mother whose infant is known to be D negative is not a candidate for RhIg. Also, mothers who have been previously immunized to D are not candidates for RhIg.
Of the following, what is the recommended routine testing to be performed on a newborn of a group B Rh positive female? The correct answer is highlighted below ABO and Rh testing would routinely be performed in this scenario. ABO, Rh and DAT would routinely be performed in this scenario. ABO, Rh and antibody screening would routinely be performed in this scenario. ABO/Rh, DAT and/or antibody screening are NOT routinely performed in this scenario.
Hemolytic Disease of the Fetus and Newborn caused by antibodies in the ABO system is typically caused by anti-A, anti-B, and/or anti-A,B from a group O mother who gives birth to a non-O newborn. Therefore, it is acceptable practice NOT to test newborns of Rh-positive women with blood types other than group O. However, laboratories choosing this protocol typically retain cord blood for a period should it be needed. If signs of anemia present in a newborn of a non-group O, Rh-positive mother, it would be appropriate to test the newborn for ABO/Rh; a DAT would be indicated if the newborn is ABO-incompatible with the mother. An antibody screening is only necessary if the newborn is to be transfused.
An Rh negative mother has just given birth to an Rh positive baby. Her physician suspects that she has experienced a fetal-maternal hemmorhage since her rosette test was positive. Upon performing the Kleihauer-Betke stain procedure, the percentage of fetal cells is found to be 0.85%. The mother's total blood volume is 4,565 mL. What dose of Rh Immune Globulin (RhIG or RhoGam) should be administered to the mother? 1 vial 2 vials 3 vials 4 vials
Rh immune globulin, also known as RhIG or RhoGam, is used to help prevent an Rh negative mother from becoming sensitized to the D antigen from an Rh positive baby. To do this, vials of Rh Ig must be administered correctly. One full dose vial (300µg or equivalent) per 30 ml of D positive whole blood (15 ml D positive packed RBCs). To calculate how many vials are needed, the following formula can be employed: KB% x blood volume = volume of baby blood In this case: 0.85% (0.0085) x 4,565mL= 38.8 mL baby blood in maternal circulation 38.8mL / 30 mL per Rh Ig vial = 1.29 vials 1.29 vials can be rounded to 1 vial. In addition, an extra vial is always added. Therefore, 2 vials is the correct answer.
In the interest of safety, it is the policy at XYZ hospital to always add one extra 300 µg vial of RhIG, regardless if the dosage calculation is rounded up or rounded down. After performing a Kleihauer-Betke test, a technologist in the laboratory at XYZ hospital calculates the fetomaternal hemorrhage to be 45 mL of fetal whole blood. How many 300 µg vials of RhIG should be administered to this woman? The correct answer is highlighted below One Two Three Four
The calculated bleed was 45 mL of fetal whole blood, the dosage calculations would yield 1.5 vials (45 mL fetal whole blood / 30 mL) = 1.5. One vial of Rh immunoglobulin (RhIG) is used for every 30 mL of fetal whole blood (or 15mL of fetal packed cells). This number, 1.5, would be rounded to 2 and an additional vial added. Thus, the final dosage would be 3 vials (900 µg or 4500 IU). In the interests of safety, if the number to the right of the decimal point is <5, round down and add 1 vial (e.g., 1.4 = 1 +1 = 2 vials) If the number to the right of the decimal point is greater than or equal to 5, round up and add 1 vial (e.g., 1.5 = 2 +1 = 3 vials).
Which cluster of differentiation (CD) is used for the quantification of hematopoietic progenitor cells (HPC) after an HPC-apheresis collection? The correct answer is highlighted below CD34 CD4 CD8 CD2
The correct answer is CD34. HPC's are CD34+ and after an HPC-apheresis collection, the number of CD34+ cells are quantified to ensure that there are sufficient cells for successful engraftment. CD4, CD8, and CD2 are all lymphocyte surface markers.
Hemolytic anemias are diagnosed by clinical findings and laboratory test results. All of the following are lab values that are relied on to help diagnose hemolytic anemia EXCEPT? The correct answer is highlighted below Hemoglobin and/or hematocrit Retic count and RBC morphology Bilirubin and haptoglobin Fibrinogen and C-reactive protein
The correct answer is fibrinogen and C-reactive protein. While both analytes are acute phase reactants (proteins) and may be increased during hemolysis, they are NOT specifically related to hemolysis or hemolytic anemia. In hemolytic anemias, the hemoglobin and hematocrit would be decreased and would be useful in the diagnosis of hemolytic anemia. The retic count and RBC morphology would both be helpful in the assessment and diagnosis of hemolytic anemia. The retic count could indicate the bone marrows response, and the RBC morphology may indicate whether the hemolysis is intravascular or extravascular. Both bilirubin and haptoglobin aid in the diagnosis and assessment of hemolytic anemia. Bilirubin levels would be increased and haptoglobin values would be decreased, particularly in intravascular hemolysis.
All of the following cellular antigens are important to an immunohematologist EXCEPT: The correct answer is highlighted below Blood group antigens Histocompatibility antigens Haptens Autoantigens
The correct answer is haptens. Haptens are immunogens that have a molecular weight less than 10,000 daltons and usually do not elicit an immune response on their own, thus they are not considered clinically significant. Blood group antigens are important in compatibility testing for red blood cell transfusions. Histocompatibility antigens are important for compatibility testing involving nucleated cells. Autoantigens are important for all compatibility testing.
How many doses of RhIG should be administered if the calculated amount of fetal whole blood volume in maternal circulation was 28 mL? The correct answer is highlighted below 1 dose 2 doses 3 doses 4 doses
When calculating RhIG dosage, facilities always add one extra dose to the calculated dose for an added margin of safety. Each dose is effective in treating 30 mL fetal whole blood. Therefore, 28 mL fetal whole blood would require one dose, plus one additional dose.
For which of the following antibodies is the DAT most likely to be NEGATIVE when testing a newborn for possible HDFN? The correct answer is highlighted below Anti-A,B Anti-c Anti-D Anti-K Feedback
While the DAT is positive in many cases of ABO HDFN, the DAT is most likely to be negative in ABO HDFN versus the other options. It's possible that the washing done as part of the DAT may break the bonds between anti-A,B and the newborn's poorly developed A (or B) antigens. Alloantibody HDFN, such as anti-D, anti-c, or anti-K is more likely to yield a positive DAT.
While working at a blood bank laboratory, you hear chimes over the hospital loudspeaker system announcing the birth of a baby. Thirty minutes later, you receive a cord blood specimen that you identify as O positive. You previously received the mother's specimen and she was O negative with a negative antibody screen. What is the next action? The correct answer is highlighted below Issue one vial of RhIg Perform a Kleihauer Betke stain Nothing - Mom is not at risk for anti-D Perform a fetal bleed screen
Because the baby is D positive and the mom is D negative and not currently immunized to the D antigen, mom will need to receive at least one 300 µg dose of RhIg. However, we must first perform a fetal bleed screen to determine if a fetal-maternal hemorrhage (FMH) has occurred. If a FMH occurred, the fetal bleed screen would be positive, and a Kleihauer Betke stain is required. In some institutions, FMH is quantified with flow cytometry studies. If the FMH is 30 mL or less, 1 vial of RhIg is indicated. For a FMH larger than 30 mL, a calculation is completed to determine how many vials of RhIg must be issued.
Which of the following set of conditions would NOT allow HDFN to occur as a result of Rh incompatibility? The correct answer is highlighted below Mother Rh-negative, father Rh-positive Mother Rh-negative, baby Rh-positive Mother Rh-negative, father Rh-negative Mother Rh-negative, father Rh-unknown
If both parents are Rh-negative, the baby would also be Rh-negative, and HDFN due to Rh incompatibility would not occur. For Rh HDFN to occur, the baby must be Rh-positive and the mother Rh-negative. If the father is Rh-positive, then there is a likely probability the baby will be Rh-positive, and thus the potential for Rh HDFN. If the Rh type of the father is unknown, it is common to assume that the father is Rh-positive due to statistical probability, and thus the potential for Rh HDFN exists.
Of the following blood group antibodies, which has been most frequently associated with severe cases of hemolytic disease of the fetus and newborn (HDFN)? The correct answer is highlighted below Anti-A,B Anti-Lea Anti-K Anti-M
Of those listed, anti-K is most frequently associated with severe forms of HDFN. Anti-K is considered the most clinically significant antibody outside of the Rh system. Kell antigens are found on both immature and mature red blood cells leading to destruction of precursor and circulating red blood cells. Anti-A,B is frequently implicated in HDFN, but the disease is generally mild, often subclinical. Anti-Lea is not implicated in HDFN for two reasons; the antibody is generally IgM and the Lewis system antigens are poorly developed at birth. Anti-M is not usually implicated in HDFN due to the fact that more anti-M is IgM.
The immunoglobulin class responsible for the etiology of Hemolytic Disease of the Fetus and Newborn (HDFN) is: The correct answer is highlighted below IgM IgG IgD IgE
The IgG class of immunoglobulins is the class associated with Hemolytic Disease of the Fetus and Newborn (HDFN). IgG is the smallest immunoglobulin class, MW 150,000. Antibodies to IgG subclasses, IgG1, IgG3, and IgG2 , are the immunoglobulins selectively transported from the maternal circulation to the fetal circulation through the placenta. Placental transfer is variable with the IgG2 subclass. In the third trimester, IgG is efficiently transported across the placenta from mother to fetus. It is now generally accepted that a cellular receptor, neonatal Fc receptor (FcRn), is pivotal for maternofetal IgG transport. Immune antibodies are formed in the mother due to antigenic stimulation. In hemolytic disease of the fetus and newborn (HDFN), maternal IgG antibodies can coat the erythrocytes of the fetus if fetal antigens specific to the maternal antibodies are present. This antigen-antibody reaction results in hemolysis primarily of erythrocytes. IgM has a molecular weight of 900,000. It is not associated with placental transfer from the mother to the fetus because of molecular size. IgD has a molecular weight of 180,000. It is not associated with placental transfer from the mother to the fetus because of molecular size. IgE has a molecular weight of 200,000. It is not associated with placental transfer from the mother to the fetus because of molecular size.
What is the Kleihauer-Betke test used for? The correct answer is highlighted below Screen for sickle cell anemia Screen for fetal hemoglobin Differentiate between maternal and fetal red cells Screen for hemoglobin A1c
The Kleihauer-Betke test allows the differentiation of fetal and maternal red cells. The Kleihauer-Braun-Betke stain is based on the principle that fetal hemoglobin is resistant to acid elution, while adult hemoglobin is not. A smear of maternal blood is treated with acid, rinsed and counterstained. Fetal cells will stain and appear pink. Maternal cells appear as ghost cells. Generally, 2000 cells are counted and the number of fetal cells determined. The hemorrhage is estimated using the following formula: Fetal cells X maternal blood volume* / Total cells counted = Fetomaternal hemorrhage (mL of whole blood) * Maternal blood volume is estimated at 5000 mL
What is the principle of the Kleihauer-Betke test? The correct answer is highlighted below The Kleihauer-Betke test capitalizes on the resistance of fetal hemoglobin to alkaline treatment. The Kleihauer-Betke test capitalizes on the resistance of fetal hemoglobin to acid treatment. The Kleihauer-Betke test capitalizes on the resistance of fetal hemoglobin to enzymatic treatment. The Kleihauer-Betke test capitalizes on the resistance of fetal hemoglobin to radiation treatment.
The Kleihauer-Betke test is based on the principle that red cells containing adult hemoglobin are more susceptible to acid elution than those containing fetal hemoglobin. A thin smear of maternal blood is treated with acid, rinsed, and counterstained. The maternal red cells, predominately adult hemoglobin, appear as pale 'ghost' cells, and the fetal red cells, predominately fetal hemoglobin, are pink. The principle of the Kleihauer-Betke is not based upon fetal hemoglobin resistance to alkaline treatment, enzymatic treatment, or radiation treatment.
What is the cause of neonatal alloimmune thrombocytopenia (NAIT)? Please select the single best answer Destruction of a neonate's platelets by alloantibodies crossing the placenta from the mother. Destruction of a neonate's platelets by an antibody that is produced by the neonate's own immune system. Decreased platelet production in the neonate. Destruction of a mother's platelets by alloantibodies crossing the placenta from the neonate.
The correct answer is destruction of a neonate's platelets by alloantibodies crossing the placenta from the mother. Neonatal alloimmune thrombocytopenia (NAIT) is caused by platelet destruction that is the result of alloantibodies stimulated by foreign antigens during pregnancy or blood transfusions. Platelet destruction by alloantibodies may occur in neonates if the mother lacks the platelet-specific antigen but the baby has inherited the antigen from its father. When maternal IgG antiplatelet antibodies cross the placenta, immune destruction of the neonate's platelets occurs. The antibodies that are produced are maternal and not neonatal. NAIT is a thrombocytopenia that is caused by increased destruction of platelets and not by decreased platelet production.