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Rh Blood group Flashcards

1
Q

What are the five principal antigens within the Rh blood group system?

A
  • D
  • C
  • c
  • E
  • e
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2
Q

What is the significance of the D antigen in the Rh blood group system?

A

D antigen found in 85% of the population; causes most clinical transfusion issues

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3
Q

What are the major theories of inheritance for the Rh blood group system?

A
  • Fisher-Race Theory
  • Wiener Theory
  • Tippett Theory
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4
Q

List instances when weak D status must be determined.

A
  • Pretransfusion testing
  • Obstetric patients
  • Blood donors
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5
Q

Describe the difference between Rhnull and Rhmod.

A
  • Rhnull: Complete absence of Rh antigens
  • Rhmod: Weakened expression of Rh antigens
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6
Q

True or False: Anti-D can cause severe hemolytic disease of the newborn (HDN).

A

True

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7
Q

List the major Rh antigens according to Rosenfield terminology.

A
  • Rh1: D
  • Rh2: C
  • Rh3: E
  • Rh4: c
  • Rh5: e
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8
Q

What is the most common D positive genotype?

A

R1r

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9
Q

What are the causes of false positive Rh results?

A

Non-specific agglutination or testing errors

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10
Q

What percentage of the population lacks the D antigen?

A

15%

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11
Q

What is the commonality of genotype DCe?

A

DCe is more common than DcE.

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12
Q

What is Rh Phenotyping used for?

A

Parentage testing, predicting HDFN, confirmation of Rh antibody specificity, locating compatible blood.

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13
Q

What does agglutination indicate in Rh Phenotyping?

A

It indicates the presence of antigen on the cell and determines phenotype.

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14
Q

What is the role of molecular testing in blood grouping?

A

It differentiates antigens and can be used for fetal genotyping.

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15
Q

What happens in D negative individuals regarding the RHD gene?

A

The RHD gene is deleted.

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16
Q

What antigens does the RHCE gene produce?

A

C, c, E, e antigens.

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17
Q

What is the most common Rh antibody?

A

Anti-D.

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18
Q

What type of antibodies are Rh antibodies?

A

They are commonly IgG.

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19
Q

How are Rh antibodies enhanced?

A

By high protein solutions, low-ionic strength saline, proteolytic enzymes, and polyethylene glycol.

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20
Q

What is the purpose of Rh immune globulin (RhIG)?

A

To protect D-negative mothers from producing anti-D antibodies.

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21
Q

When is RhIG administered?

A

At 28 weeks gestation and within 72 hours of delivery of an Rh positive baby.

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22
Q

What is weak D expression due to?

A
  • Genetic variation of D gene * Position effect * Partial D.
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23
Q

What does weak D indicate about D antigen expression?

A

Weakened expression of D antigen.

24
Q

What are the three ways weak D phenotype can occur?

A
  • Positional * Mosaic * Genetic.
25
What is the significance of weak D in blood donors?
Weak forms are less immunogenic and must be investigated in first-time Rh-negative donors.
26
What is the standard practice for transfusing Rh negative patients?
To transfuse with Rh negative blood.
27
What are compound antigens in the context of Rh blood group?
C and e antigens occurring in cis.
28
List the four compound antigens in the Rh system.
* f (ce) * r1 (Ce) * cE * CE
29
What happens when c and e are inherited as a haplotype?
Another determinant or epitope called 'f' is inherited, which can elicit its own immune response.
30
True or False: DCe/Dce would form f if c and e are inherited on opposite chromosomes.
False.
31
What is the impact of high protein, low–ionic strength solutions on Rh antibodies?
They enhance the agglutination of Rh antibodies.
32
What are low incidence Rh antigens?
Antigens that occur in 1% - 2% of the random population or less.
33
Give an example of a low incidence Rh antigen and its frequency in Whites and Blacks.
Cw = low frequency Ag found in approx 2% of Whites and 1% of Blacks.
34
What are high incidence Rh antigens?
Antigens that occur in greater than 99% of the population.
35
What is the purpose of Rh control in transfusion?
To detect false positive reactions due to autoagglutination in high protein antisera.
36
What must Rh control contain?
Everything the manufacturer has added except the Rh antibody.
37
What should be done if the Rh control is positive?
Perform a DAT to determine if uptake of alloantibody or autoantibody is causing the positive result.
38
What is the consequence of using high-protein reagents with a positive DAT?
They can cause false positive anti-D testing.
39
What is the role of chemically modified anti-D?
It increases the span of its Fab fragments for agglutination.
40
What is the most frequent cause of false positive Rh typing?
Spontaneous agglutination of DAT positive cells.
41
What should be checked if the Rh typing is positive for both patient and control?
Re-type the patient with low-protein reagents.
42
What is a corrective action for a cell suspension that is too heavy?
Adjust suspension then re-type patient.
43
What should be done if there is interference from cold agglutinins?
Use pre-warmed technique then re-type.
44
What should you never do with droppers in a laboratory setting?
Never touch or lay dropper down on work bench; always replace dropper immediately after use.
45
What should you always do before using reagents?
Read labels; never use reagents if label is missing or unreadable.
46
What is a common cause of false-negative Rh typing?
Antibody coated RBC’s in vivo.
47
Fill in the blank: Always add _______ to the test before the addition of cells.
anti-serum
48
What is the recommended action when reagent deterioration is suspected?
Re-type using fresh reagent.
49
What type of antibodies usually appear after exposure to Rh antigens?
Most are of the IgG class.
50
True or False: Rh antibodies bind complement.
False
51
What is the significance of a second exposure to Rh antigens?
It will produce a RAPID secondary immune response (anamnestic).
52
List the order of immunogenicity for Rh antibodies from most to least.
* D * c * E * C * e
53
Fill in the blank: If an Rh typing problem is detected, _______ blood must be administered until resolved.
Rh Negative
54
What can cause false positive results in the Rh control?
Presence of AUTOAGGLUTININS or unwashed RBCs when rouleaux is present.
55
What is the Rh null phenotype?
Individuals lack all Rh antigens on their red cells; can transmit normal Rh antigens to offspring.
56
What is the most common LW allele?
LW a
57
What is the significance of the LW blood group system?
It must be considered when investigating mosaic D.

Transfusion (12 decks)

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