RHIG Calculations Flashcards

*Question: What is the generic name of RhoGAM?
A) Rh₀(D) immune serum
B) Rh₀(D) immune globulin
C) Anti-D immunoglobulin M
D) D-antigen immune concentrate

*Answer: B) Rh₀(D) immune globulin

*Question: What class of antibody is RhIG composed of?
A) IgM
B) IgA
C) IgE
D) IgG

*Answer: D) IgG

*Question: What is the mechanism of action of RhIG?
A) Neutralizes Anti-D antibodies in fetal circulation
B) Stimulates maternal production of blocking antibodies
C) Opsonizes Rh-positive cells for clearance by splenic macrophages
D) Inhibits complement activation on fetal red blood cells

*Answer: C) Opsonizes Rh-positive cells for clearance by splenic macrophages

*Question: RhIG is administered to which type of patient?
A) Rh-positive mothers carrying Rh-negative babies
B) Rh-negative mothers carrying Rh-positive babies
C) Rh-positive mothers carrying Rh-positive babies
D) All pregnant women regardless of Rh type

*Answer: B) Rh-negative mothers carrying Rh-positive babies

*Question: A standard 300-μg vial of RhIG can suppress the immune response to how many mL of Rh-positive RED BLOOD CELLS?
A) 30 mL
B) 10 mL
C) 15 mL
D) 50 mL

*Answer: C) 15 mL

*Question: A standard 300-μg dose of RhIG covers up to how many mL of fetal WHOLE BLOOD?
A) 15 mL
B) 20 mL
C) 50 mL
D) 30 mL

*Answer: D) 30 mL

*Question: At what gestational age is the routine antepartum dose of RhIG administered?
A) 20 weeks
B) 24 weeks
C) 28 weeks
D) 32 weeks

*Answer: C) 28 weeks

*Question: Why is RhIG given at 28 weeks gestation?
A) Because fetal Rh type is confirmed at this point
B) Because most sensitization to the D antigen occurs at or after 28 weeks
C) Because placental transfer of IgG begins at 28 weeks
D) Because fetal blood volume peaks at 28 weeks

*Answer: B) Because most sensitization to the D antigen occurs at or after 28 weeks

*Question: Within how many hours of delivery must the postpartum RhIG dose be administered?
A) 24 hours
B) 48 hours
C) 72 hours
D) 96 hours

*Answer: C) 72 hours

*Question: If the 72-hour postpartum window for RhIG administration is missed, what should be done?
A) RhIG is no longer effective and should not be given
B) Double the dose and administer within 1 week
C) Give RhIG as soon as possible as it may still offer protection
D) Perform a direct antiglobulin test before proceeding

*Answer: C) Give RhIG as soon as possible as it may still offer protection

*Question: What does a NEGATIVE Rosette test indicate?
A) FMH is greater than 30 mL
B) FMH is less than 10 mL and one vial is sufficient
C) No RhIG is needed
D) KB test must be performed immediately

*Answer: B) FMH is less than 10 mL and one vial is sufficient

*Question: What happens when the Rosette test is POSITIVE?
A) Administer 2 vials automatically
B) Repeat the Rosette test for confirmation
C) Quantify FMH using KB test or flow cytometry
D) Withhold RhIG and monitor the mother

*Answer: C) Quantify FMH using KB test or flow cytometry

*Question: What is the principle behind the Rosette test?
A) Fetal cells lyse maternal RBCs forming visible zones
B) Indicator cells form rosettes around fetal Rh-positive RBCs
C) Acid elution removes hemoglobin from maternal cells only
D) Anti-D antibodies agglutinate fetal cells in a rosette pattern

*Answer: B) Indicator cells form rosettes around fetal Rh-positive RBCs

*Question: Which test is the gold standard for QUANTIFYING fetomaternal hemorrhage?
A) Rosette test
B) Direct Antiglobulin Test
C) Kleihauer-Betke acid elution test or flow cytometry
D) Indirect Antiglobulin Test

*Answer: C) Kleihauer-Betke acid elution test or flow cytometry

*Question: In the Kleihauer-Betke test, how do fetal red blood cells appear?
A) Ghost cells with no staining
B) Pale/lysed cells
C) Dark pink due to acid-resistant fetal hemoglobin
D) Blue cells due to alkaline staining

*Answer: C) Dark pink due to acid-resistant fetal hemoglobin

*Question: Why is flow cytometry preferred over the KB test?
A) It is cheaper and faster
B) KB test cannot detect any fetal cells
C) KB test is subject to human error and less precise
D) Flow cytometry uses acid elution for better sensitivity

*Answer: C) KB test is subject to human error and less precise

*Question: What is the minimum percentage of fetal red cells the KB test can detect?
A) 0.1%
B) 1.0%
C) 0.5%
D) 2.0%

*Answer: C) 0.5%

*Question: What is the total number of cells always counted in the KB test for RhIG calculations?
A) 500
B) 1,000
C) 5,000
D) 2,000

*Answer: D) 2,000

*Question: What is the average maternal blood volume used in RhIG calculations?
A) 3,500 mL
B) 4,000 mL
C) 5,000 mL
D) 6,000 mL

*Answer: C) 5,000 mL

*Question: What divisor is used when calculating the number of RhIG vials from FMH volume?
A) 15 mL/vial
B) 20 mL/vial
C) 25 mL/vial
D) 30 mL/vial

*Answer: D) 30 mL/vial

*Question: After calculating the number of vials and rounding, what must ALWAYS be done?
A) Subtract one vial if the decimal was less than 0.5
B) Add one additional vial as a safety margin
C) Double the vials if KB test was used
D) Confirm with a repeat Rosette test

*Answer: B) Add one additional vial as a safety margin

*Question: A KB stain shows 32 fetal cells out of 2,000 total cells. What is the percentage of fetal cells?
A) 0.32%
B) 3.2%
C) 1.6%
D) 0.16%

*Answer: C) 1.6%

*Question: Using a maternal blood volume of 5,000 mL and 1.6% fetal cells, what is the estimated FMH volume?
A) 40 mL
B) 160 mL
C) 80 mL
D) 800 mL

*Answer: C) 80 mL

*Question: An FMH of 80 mL divided by 30 mL/vial gives 2.67. After rounding and adding the safety margin, how many vials are needed?
A) 2
B) 3
C) 4
D) 5

*Answer: C) 4

*Question: A KB stain shows 58 fetal cells per 2,000. MBV is 5,000 mL. How many RhIG vials are needed?
A) 4
B) 5
C) 6
D) 7

*Answer: C) 6

*Question: A KB stain identifies 22 fetal cells per 2,000. MBV is 4,500 mL. How many vials are required?
A) 2
B) 3
C) 4
D) 1

*Answer: B) 3

*Question: A KB stain shows 120 fetal cells per 2,000 total cells. MBV is 4,600 mL. What is the FMH volume?
A) 138 mL
B) 276 mL
C) 552 mL
D) 230 mL

*Answer: B) 276 mL

*Question: An FMH of 276 mL divided by 30 mL/vial = 9.2. After applying rounding rules and safety margin, how many vials are given?
A) 9
B) 10
C) 11
D) 12

*Answer: B) 10

*Question: In HDFN, which pregnancy is typically when the mother first produces Anti-D?
A) Never — mothers produce Anti-D naturally
B) Second pregnancy
C) First pregnancy
D) Third pregnancy

*Answer: C) First pregnancy

*Question: A calculated vial count yields 4.4 before adding the safety margin. What is the final number of vials to administer?
A) 4
B) 5
C) 6
D) 3

*Answer: B) 5

*Question: Which of the following best describes the Rosette test's role in RhIG dosing?
A) It precisely determines the number of vials needed
B) It is a quantitative test that replaces the KB test
C) It is a screening test that determines whether further quantification is necessary
D) It measures maternal anti-D titers postpartum

*Answer: C) It is a screening test that determines whether further quantification is necessary