Meh hemolytic: Rh, ABO, Kell, Duffy, Kidd 12-18 (1)

Question 1

~85% of people have Rh antigen on their RBCs – i.e., Rh(+).

Answer 1

.

Question 2

Women who are in the ~15% that are Rh(-) are at risk of developing IgG antibodies against Rh antigen if the fetus is Rh(+) and the circulations mix inadvertently.

Answer 2

.

Question 3

“Rh isoimmunization.” what does that mean?

Answer 3

When the mother develops antibodies against Rh (i.e., has become sensitized to it).

Question 4

NBME will throw
“Rh isoimmunization.” word around a bit, so
you need to know it means “she’s developed IgG antibodies against Rh.”

Answer 4

.

Question 5

Mechanism is Rh isommunization?

Answer 5

Rh(-) mom in first pregnancy is exposed to fetal blood that is Rh(+);
mom makes Abs against Rh;
subsequent pregnancy results in IgG against Rh
crossing placenta and targeting fetal Rh(+) RBCs, leading to hemolysis in the fetus.

Question 6

when is checked Rh status? weeks

Answer 6

At the first antenatal screening at 8-10 weeks.

Question 7

If the mother is Rh(-), then give RhoGAM at what 2 points?

Answer 7

28 weeks as well as at
parturition.

Question 8

If the mother is Rh(-), RhoGAM is also should be given when what procedures/abortions?

Answer 8

It must also be given if there are any interventions (e.g.,
amniocentesis), or if there’s complications like spontaneous abortion or abruptio placentae.

Question 9

If 2nd pregnancy onward, if Rh (-) woman is found to have titers against Rh, what’s about RhOGAM?

Answer 9

do not give RhoGAM during the pregnancy, since it’s too late.

Question 10

what tests is done in setting of hemorrhage or suspected mixing of
maternal and fetal circulations in Rh(-) women.?

Answer 10

Kleihauer-Betke (KB) test

Question 11

Kleihauer-Betke (KB) test. when is done?

Answer 11

in setting of hemorrhage or suspected mixing of
maternal and fetal circulations in Rh(-) women

Question 12

Kleihauer-Betke (KB) test. The mother’s blood is drawn, and
the test works by exploiting the resistance of HbF to acid, allowing fetal RBCs to be distinguished from maternal cells on a blood smear. Depending on the fraction of fetal RBCs present, this determines the dose of RhoGAM necessary.

Answer 12

.

Question 13

ABO type.
Most anti-A and -B Abs people have to opposing blood types are IgM, but people
with O blood can have fractionally greater IgG;

Answer 13

if mother with O blood has higher % of anti-A and -B Abs that are IgG, fetus can be symptomatic.

Question 14

ABO type.
USMLE will give you O+ mom usually in first pregnancy and A or B fetus (can occur
in Rh- women in second pregnancies, but the USMLE wants to assess you specifically know the ABO type of HDN, so they’ll give O+ mom in first pregnancy).

Answer 14

.

Question 15

Kell, Duffy, Kidd type.
Minor antigens beyond Rh (i.e., Kell, Duffy, Kidd) can sometimes cause HDN.

Answer 15

.

Question 16

Kell, Duffy, Kidd type. The process for isoimmunization is same as Rh.

Answer 16

.

Question 17

Kell, Duffy, Kidd type. an A+/B+/AB+ mother will have a second pregnancy where
fetal hemolysis is occurring.

Answer 17

but based on her blood type, you know it’s not ABO or Rh type HDN.

Question 18

Kell, Duffy, Kidd type. The Q will say her blood titer for, e.g., Kell is high. The next best step?

Answer 18

“check Kell status of the father.”

Question 19

Kell, Duffy, Kidd type.

Answer 19

In other words, since the mother has titers against Kell, you know she’s Kell negative. So if the father’s RBCs are Kell(+), the fetus is likely Kell(+), and that would
explain the HDN.