9 HEMOLYTIC DISEASE OF THE FETUS AND NEWBORN

Question 1

(1) All of the following are reasons for a positive DAT on cord blood cells of a newborn except:

A. High concentrations of Wharton jelly on cord blood cells
B. Immune anti-A from an O mother on the cells of an A baby
C. Immune anti-D from an Rh negative mother on the cells of an Rh-positive baby
D. Immune anti-K from a K-negative mother on the cells of a K-negative baby

Answer 1

D. Immune anti-K from a K-negative mother on the cells of a K-negative baby

Immune anti-K from the mother would not coat the baby’s RBCs if they did not contain the K antigen; therefore, the DAT result would be negative.

Question 2

(2) A fetal screen yielded negative results on a mother who is O negative and infant who is O positive. What course of action should be taken?

A. Perform a Kleihauer-Betke test
B. Issue one full dose of RhIg
C. Perform a DAT on the infant
D. Perform an antibody screen on the mother

Answer 2

B. Issue one full dose of RhIg

If the fetal screen or rosette test has a negative result, indicating the fetal maternal blood is negligible in a possible RhIg candidate, standard practice is to issue one dose of RhIg

Question 3

(3) What should be done when a woman who is 24 weeks pregnant has a positive antibody screen?

A. Perform an antibody identification panel; titer, if necessary
B. No need to do anything until 30 weeks’ gestation
C. Administer RhIg
D. Adsorb the antibody onto antigen-positive cells

Answer 3

A. Perform an antibody identification panel; titer, if necessary

The identification of the antibody is very important at this stage of the pregnancy. If the antibody is determined to be clinically significant, then a titer may determine the strength of the antibody and the need for clinical intervention.

Question 4

(4) All of the following are interventions for fetal distress caused by maternal antibodies attacking fetal cells except:

A. Intrauterine transfusion
B. Plasmapheresis on the mother
C. Transfusion of antigen-positive cells to the mother
D. Middle cerebral artery peak systolic velocity (MCA-PSV)

Answer 4

C. Transfusion of antigen-positive cells to the mother

Transfusion of antigen-positive cells to the mother who already has an antibody might cause a transfusion reaction and/or evoke an even stronger antibody response, possibly causing more harm to the fetus.

Question 5

(5) Cord blood cells are washed six times with saline, and the DAT result and negative control are still positive. What should be done next?

A. Obtain a heelstick sample
B. Record the DAT result as positive
C. Obtain another cord blood sample
D. Perform elution on the cord blood cells

Answer 5

A. Obtain a heelstick sample

If the cord blood cells contain excessive Wharton jelly, then further washing or obtaining another cord blood sample will not solve the problem. A heelstick sample will not contain Wharton jelly and should give a valid DAT result.

Question 6

(6) What can be done if HDFN is caused by maternal anti-K?

A. Give Kell immune globulin
B. Monitor the mother’s antibody level
C. Prevent formation of K-positive cells in the fetus
D. Not a problem; anti-K is not known to cause HDFN

Answer 6

B. Monitor the mother’s antibody level

Anti-D is the only antibody for which prevention of HDFN is possible. If a pregnant woman develops anti-K, she will be monitored to determine if the antibody level and signs of fetal distress necessitate clinical intervention.

Question 7

(7) Should an O-negative mother receive RhIg if a positive DAT on the newborn is caused by immune anti-A?

A. No, the mother is not a candidate for RhIg because of the positive DAT result
B. Yes, if the baby’s type is Rh negative
C. Yes, if the baby’s type is Rh positive
D. No, the baby’s problem is unrelated to Rh blood group antibodies

Answer 7

C. Yes, if the baby’s type is Rh positive

RhIg is immune anti-D and is given to Rh-negative mothers who give birth to Rh-positive babies and who do not have anti-D already formed from previous pregnancies or transfusion.

Question 8

(8) Should an A-negative woman who has just had a miscarriage receive RhIg?

A. Yes, but only if she does not have evidence of active anti-D
B. No, the type of the baby is unknown
C. Yes, but only a minidose regardless of trimester
D. No, RhIg is given to women at full-term pregnancies only

Answer 8

A. Yes, but only if she does not have evidence of active anti-D

When the fetus is Rh positive or the Rh status of the fetus is unknown, termination of a pregnancy from any cause presents a situation in which an Rh-negative patient should receive RhIg. A minidose is used if the pregnancy is terminated in the first trimester.

Question 9

(9) SITUATION:. The automated blood bank analyzer reports a type of O negative on a woman who is 6 weeks pregnant with vaginal bleeding. The woman tells the emergency department physician she is O positive and presents a blood donor card. The MLS performs a test for weak D and observes a 1+ reaction in the AHG phase. The Kleihauer-Betke test result is negative. Is this woman a candidate for RhIg?

A. Molecular testing is indicated to ascertain the type of weak D
B. Yes, she is Rh positive
C. No, there is no evidence of a fetal bleed
D. Yes, based on the automated typing results

Answer 9

A. Molecular testing is indicated to ascertain the type of weak D

The negative Kleihauer-Betke test result confirms that the positive reaction of the woman’s RBCs with anti-D at the IAT phase is not the result of fetal maternal bleeding. The woman is weak D positive and, therefore, requires molecular testing to discern if she is a candidate for RhIg. Weak D types 1, 2, 3, and 4 do not make anti-D and do not require RhIg prophylaxis

Question 10

(10) Which of the following patients would be a candidate for RhIg?

A. B-positive mother; B-negative baby; first pregnancy; no anti-D in mother
B. O-negative mother; A-positive baby; second pregnancy; no anti-D in mother
C. A-negative mother; O-negative baby; fourth pregnancy; anti-D in mother
D. AB-negative mother; B-positive baby; second pregnancy; anti-D in mother

Answer 10

B. O-negative mother; A-positive baby; second pregnancy; no anti-D in mother

An O-negative mother who gives birth to an A-positive baby and has no anti D formed from a previous pregnancy would be a candidate for RhIg. A mother who already has active anti-D or a mother who gives birth to an Rh negative baby is not a candidate for RhIg. Anti-D formation via active immunization typically has a titer greater than 4, compared with passive administration of anti-D, which has a titer less than 4.

Question 11

(11) The Kleihauer-Betke acid elution test identifies 40 fetal cells in 2,000 maternal RBCs. How many full doses of RhIg are indicated?

A. 1
B. 2
C. 3
D. 4

Answer 11

D. 4

To calculate the number of vials of RhIg to infuse, divide 40 by 2,000, and multiply by 5,000. This gives the estimated total blood volume of the mother in milliliters. Divide this number by 30 to obtain the number of doses. When the number to the right of the decimal point is less than 5, round down, and add one dose of RhIg. Conversely, when the number to the right of the decimal point is 5 or greater, round up, and add one dose of RhIg. In this example, the number of doses is 3.3. Rounding down and adding one vial gives an answer of four vials.

Question 12

(12) Kernicterus is caused by the effects of:

A. Anemia
B. Unconjugated bilirubin
C. Antibody specificity
D. Antibody titer

Answer 12

B. Unconjugated bilirubin

Kernicterus occurs because of high levels of unconjugated bilirubin. High levels of this pigment cross into the central nervous system, causing brain damage to the infant.

Question 13

(13) Anti-E is detected in the serum of a woman in the first trimester of pregnancy. The first titer for anti-E is 32. Two weeks later, the antibody titer is 64 and then 128 after another 2 weeks. Clinically, there are beginning signs of fetal distress. What may be done?

A. Induce labor for early delivery
B. Perform plasmapheresis to remove anti-E from the mother
C. Administer RhIg to the mother
D. Perform an intrauterine transfusion using E-negative cells

Answer 13

B. Perform plasmapheresis to remove anti-E from the mother

Plasmapheresis removes excess anti-E from the mother and provides a temporary solution to the problem until the fetus is mature enough to be delivered. The procedure may need to be performed several times, depending on how quickly and how high the levels of anti-E rise. Administration of RhIg would not contribute to solving this problem caused by anti-E. Intrauterine transfusion would not be performed before week 20 and would be considered only if there is evidence of severe hemolytic disease.

Question 14

(14) What testing is done for exchange transfusion when the mother’s serum contains an alloantibody?

A. Crossmatching and antibody screen
B. ABO, Rh, antibody screen, and crossmatching
C. ABO, Rh, antibody screen
D. ABO and Rh only

Answer 14

B. ABO, Rh, antibody screen, and crossmatching

ABO (forward) and Rh are required. An antibody screen using either the neonatal serum or maternal serum is required. Crossmatching is necessary as long as maternal antibody persists in the infant’s blood.

Question 15

(15) Which blood type may be transfused to an AB-positive baby who has HDFN caused by anti-D?

A. AB negative, CMV negative, Hgb S negative; irradiated or O negative, CMV negative, Hgb S negative
B. AB positive, CMV negative; irradiated or O positive, CMV negative
C. AB negative only
D. O negative only

Answer 15

A. AB negative, CMV negative, Hgb S negative; irradiated or O negative, CMV negative, Hgb S negative

Either AB-negative or O-negative RBCs may be given to an AB-positive baby because both types are ABO compatible and lack the D antigen.

Question 16

(16) All of the following are routinely performed on a cord blood sample except:

A. Forward ABO typing
B. Antibody screen
C. Rh typing
D. DAT

Answer 16

B. Antibody screen

An antibody screen is not performed routinely on a cord blood sample because a baby does not make antibodies until about 6 months of age. Any antibodies detected in a cord blood sample come from the mother.

Question 17

(17) Why do Rh-negative women tend to have a positive antibody screen compared with Rh-positive women of childbearing age?

A. They have formed active anti-D
B. They have received RhIg
C. They have formed anti-K
D. They have a higher rate of transfusion

Answer 17

B. They have received RhIg

The most common reason an Rh-negative woman has a positive antibody screen is because of previously receiving RhIg or passive anti-D.

Question 18

(18) SITUATION: An O-negative mother gave birth to a B-positive infant. The mother had no history of antibodies or transfusion. This was her first child. The baby was mildly jaundiced, and the DAT result was weakly positive with polyspecific antisera. What could have caused the positive DAT result?

A. Anti-D from the mother coating the infant RBCs
B. An alloantibody, such as anti-K, coating the infant RBCs
C. Maternal anti-B coating the infant RBCs
D. Maternal anti-A, B coating the infant RBCs

Answer 18

D. Maternal anti-A, B coating the infant RBCs

Anti-A,B is an IgG antibody and can cross the placenta and attach to infant cells. It is known as a single entity as opposed to separate antibodies. Anti-D would not be the cause because this is the first pregnancy. Anti-K is not the cause because there is no history of alloantibodies or past transfusions.

Question 19

(19) SITUATION: RhIg is requested on a 28-year-old woman with suspected abortion. When the nurse arrives in the blood bank to pick up the RhIg, she asks the MLS if it is a minidose. The MLS replies that it is a full dose, not a minidose. The nurse then requests to take 50 μg from the 300 μg syringe to satisfy the physician’s orders. What course of action should the MLS take?

A. Let the nurse take the syringe of RhIg, so that she may withdraw 50 μg
B. Call a supervisor or pathologist
C. Instruct the nurse that the blood bank does not stock minidoses of RhIg and manipulating the full dose will compromise the purity of the product
D. Instruct the nurse that the blood bank does not stock minidoses of RhIg, and relay this information to the patient’s physician

Answer 19

D. Instruct the nurse that the blood bank does not stock minidoses of RhIg, and relay this information to the patient’s physician

Blood banks operate by strict standard operating procedures. These include decisions about which products are supplied from the blood bank. Although B may also be a solution, D is the best answer because the patient’s physician can communicate with the pathologist once he or she receives this information from the nurse.