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Trans Lecture 4 Flashcards

Rh blood group system

1
Q

How many genetic loci determine the Rh System Inheritance?

A

Two genetic loci determine the Rh System Inheritance.

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2
Q

During which period was the inheritance of the Rh Blood Group System in question?

A

The inheritance of the Rh Blood Group System was in question from the 1940s to the 1990s.

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3
Q

Which terminology is commonly used today for the Rh System Inheritance?

A

The terminology that is part of the Fisher-Race Theory is most commonly used even today.

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4
Q

How are genes coding for the Rh system inherited?

A

Genes coding for the Rh system are inherited as haplotypes, which are close together on the same chromosome.

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5
Q

How many genes are closely inherited on the same locus?

A

Three genes are closely inherited on the same loci.

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6
Q

How can you predict the probability of D-positive offspring?

A

You can predict the probability of D-positive offspring from a D-negative mother and a heterozygous father.

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7
Q

Is the gene ‘d’ a real gene in Rh System Inheritance?

A

No, the gene ‘d’ does not exist and is used only for illustrative purposes.

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8
Q

What percentage of children could be D-positive when the mother is D-negative and father is heterozygous?

A

50% of the children could be D-positive.

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9
Q

What is the purpose of giving Rogan to Rh- mom?

A

The purpose is to prevent complications during pregnancy and childbirth.

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10
Q

When is Rogan given to Rh- mom?

A

Rogan is given to Rh- mom at 28 weeks of pregnancy.

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11
Q

How many weeks are there in a full-term pregnancy?

A

There are 40 weeks in a full-term pregnancy.

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12
Q

When is Rogan given to Rh- mom after birth if the baby is Rh+?

A

If the baby is Rh+, Rogan is given to the mom within 3 days of birth.

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13
Q

According to the Fisher-Race theory, how are the D, C, and E genes inherited?

A

D is inherited at one locus, C or c is inherited at a second locus, and E and e are inherited at the third locus.

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14
Q

How many gene complexes are there at the Rh locus according to Fisher-Race?

A

There are 8 gene complexes at the Rh locus according to Fisher-Race.

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15
Q

What is the order of gene notation according to Fisher-Race?

A

Fisher-Race uses DCE as the order for gene notation.

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16
Q

What is the difference between Wiener and Fisher-Race theories in terms of Rh System Inheritance?

A

The difference is the inheritance of the Rh system on a single gene locus vs 3 separate genes.

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17
Q

According to Wiener, how many alleles are there for the Rh antigens?

A

According to Wiener, there are 8 alleles resulting in various Rh antigens.

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18
Q

Is the Wiener terminology used as often today?

A

No, the Wiener terminology is not used as often today.

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19
Q

What do you often see when a person is considered Rh-positive?

A

You often see Rho(D) when a person is considered Rh-positive.

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20
Q

What do immunohematologists use when recording most probable genotypes?

A

Immunohematologists use combinations of both Fisher-Race and Wiener systems.

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21
Q

How should you convert a Fisher-Race notation into Wiener notation?

A

To convert a Fisher-Race notation into Wiener, you should write R0 for Dce.

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22
Q

What is the genotype for the most common D-positive genotype?

A

The most common D-positive genotype is R1r, which is DCe/dce (antibody E-).

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23
Q

What is the genotype for the most common D-negative genotype?

A

The most common D-negative genotype is rr, which is dce/dce.

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24
Q

What does ‘R’ indicate in the context of Rh System Inheritance?

A

‘R’ indicates Rh positive.

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25
Q

What does ‘(r)’ indicate in the context of Rh System Inheritance?

A

‘(r)’ indicates Rh negative.

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26
Q

What can cause red cells to agglutinate?

A

Red cells can agglutinate when they are pre-sensitized with antibody in vivo and brought close together in a high protein medium.

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27
Q

Can red cells with a positive DAT agglutinate in a high protein medium?

A

Yes, red cells with a positive DAT can agglutinate in a high protein medium.

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28
Q

What can cause a false positive in D typing?

A

If red cells already have antibody on them, the high protein in the anti-D can bring the cells close together, forming cross-bridges and causing a false positive result.

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29
Q

How can the Rh(D) type be determined if the Rh control is positive?

A

If the Rh control is positive, the Rh(D) type must be determined using a low protein anti-D serum.

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30
Q

What is the composition of saline anti-D?

A

Saline anti-D contains IgM anti-D suspended in a protein concentration of about 6 - 8% albumin.

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31
Q

When is saline anti-D usually used?

A

Saline anti-D is usually used to D type red cells that give a positive Rh control when tested with slide and modified tube anti-D or cells with a positive DAT.

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32
Q

Why is saline anti-D considered an expensive antiserum?

A

Saline anti-D is considered expensive because donors producing IgM anti-D are hard to find.

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33
Q

Can saline anti-D be used for weak D (Du) typing?

A

No, saline anti-D cannot be used for weak D (Du) typing as it is IgM and weak D typing requires IgG.

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34
Q

What are the characteristics of chemically modified anti-D?

A

Chemically modified anti-D contains IgG anti-D that has been chemically modified to increase the span of its Fab fragments and a low protein concentration of 6 - 8%.

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35
Q

How is chemically modified anti-D made?

A

Chemically modified anti-D is made by treating IgG anti-D with sulfhydryl agents to split the interchain disulphide bonds and allow wider distance agglutination.

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36
Q

What can serve as a control for chemically modified anti-D typing?

A

The forward ABO group or an Rh control of 6% albumin can serve as a control for chemically modified anti-D typing.

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37
Q

When is monoclonal/polyclonal anti-D used?

A

Monoclonal/polyclonal anti-D can be used as an alternative to saline anti-D for typing red cells with a positive DAT, for routine D typing, and for weak D (Du) typing.

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38
Q

What are the characteristics of monoclonal/polyclonal anti-D?

A

Monoclonal/polyclonal anti-D blends contain monoclonal IgM and polyclonal IgG anti-D, and require 6% albumin as an Rh control.

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39
Q

What reagent has replaced saline anti-D?

A

Chemically modified reagent has replaced saline anti-D for typing red cells with a positive DAT.

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40
Q

Why is a control necessary in Rh typing?

A

A control is necessary because heavily sensitized red cells may spontaneously agglutinate even in low protein media, such as is present in anti-A, anti-B, and saline anti-D.

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41
Q

What is the most common position effect in weak D caused by?

A

Weak D caused by C inherited in trans.

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42
Q

What happens to D-antigen expression when the D and C genes are inherited on the opposite chromosome?

A

The D-antigen expression will be weaker.

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43
Q

What are the two types of weak D?

A

CIS and TRANS.

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44
Q

What happens in CIS weak D?

A

Both genes are inherited on the same chromosome.

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45
Q

What happens in TRANS weak D?

A

The genes are inherited on different chromosomes.

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46
Q

Why would today’s weak D type as a regular D?

A

Due to the sensitivity of the monoclonal reagents.

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47
Q

What is an example of CIS Du?

A

Phenotype R1r’ (CDe/Ce).

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48
Q

What is an example of TRANS Du?

A

Phenotype R0r’ (cDe/Ce).

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49
Q

What gene takes over in TRANS Du?

A

The C gene takes over.

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50
Q

What is weakened in TRANS Du?

A

The D antigen.

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51
Q

What is missing in weak D-Mosaic/Partial D?

A

Some components of the D antigen are missing.

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52
Q

What happens if a patient with weak D is transfused with D positive blood?

A

They may develop an anti-D alloantibody to the missing part of the antigen.

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53
Q

What may happen if anti-D reagents from 2 different manufacturers do not agree?

A

Suspect partial or mosaic D.

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54
Q

Why should weak forms of D antigen be investigated in blood donors?

A

They are substantially less immunogenic than normal D positive blood.

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55
Q

What is standard practice for transfusion in Rh-negative donors?

A

To investigate all blood donors for weak D or all first-time Rh-negative donors.

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56
Q

What should be done if a weak D is positive in blood donors?

A

The units should be labelled as Rh Positive.

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57
Q

What does weak D cause in patients with anti-D?

A

Severe hemolytic transfusion reaction (HTR).

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58
Q

What can blood recipients with weak D develop when transfused with D positive blood?

A

An anti-D alloantibody to the missing part of the antigen.

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59
Q

What happens if the direct agglutination test with commercial anti-D is negative for weak D?

A

No longer common practice to investigate for a possible weak D.

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60
Q

How are patients with weak D typically typed?

A

As Rh negative and will receive Rh negative blood.

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61
Q

What are compound antigens in the Rh system?

A

Antigens that occur when two alleles are inherited on the same gene.

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62
Q

What is an example of a compound antigen in the Rh system?

A

f (ce), r1 (Ce), cE, CE.

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63
Q

What happens if an individual has an anti-f?

A

It would only react with f positive cells and not cells positive for c or e in trans.

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64
Q

What is the significance of f cells in testing for compound antigens?

A

They are clearly marked on the antigram of screen and panel cells.

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65
Q

What is a cis-product antigen?

A

The product of two alleles inherited on the same gene.

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66
Q

How many compound antigens are there in the Rh system?

A

There are 4 compound antigens.

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67
Q

What is the significance of antibodies to compound antigens?

A

They may be useful in ascertaining the exact Rh genotype.

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68
Q

How does testing the father’s Rh genotype help predict HDN likelihood?

A

Testing the father’s Rh genotype helps predict the probability of the baby being D positive and suffering from Rho HDN.

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69
Q

What is the probability of a baby being D negative if the father is also D negative?

A

If the father is D negative, the baby will also be D negative with a 0% probability of suffering from Rho HDN.

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70
Q

What is the probability of a baby being D positive and suffering from Rho HDN if the father’s Rh genotype is R1r, R2r, or Ror?

A

If the father’s Rh genotype is R1r, R2r, or Ror, the baby has a 50% probability of being D positive and suffering from Rho HDN.

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71
Q

What is the probability of a baby being D positive and suffering from Rho HDN if the father’s Rh genotype is R1R1, R2R2, R1R2, RoRo, R1Ro, or R2Ro?

A

If the father’s Rh genotype is R1R1, R2R2, R1R2, RoRo, R1Ro, or R2Ro, the baby has a 100% chance of being D positive and suffering from Rho HDN.

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72
Q

What type of antibodies are Rh antibodies?

A

Rh antibodies are commonly IgG antibodies.

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73
Q

How are Rh antibodies formed?

A

Rh antibodies are formed by immune stimulus such as transfusions or pregnancy, and are not naturally occurring.

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74
Q

What enhances the agglutination of Rh antibodies?

A

Agglutination of Rh antibodies is enhanced by high protein (albumin), low-ionic strength saline (LISS), proteolytic enzymes (ficin), and polyethylene glycol (PEG).

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75
Q

Which cells do Rh antibodies react stronger with - homozygous or heterozygous cells?

A

Rh antibodies react stronger with homozygous cells than with heterozygous cells, showing dosage.

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76
Q

What is the most common Rh antibody seen in Rh positive individuals?

A

The most common Rh antibody seen in Rh positive individuals is anti-E.

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77
Q

Which Rh antigen is difficult to find compatible blood for due to anti-e autoantibody presence?

A

Anti-e is difficult to find compatible blood for since 98% of the population have the e antigen.

78
Q

Which Rh antibodies are often seen in combination?

A

Anti-C,e or Anti-c,E are often seen in combination.

79
Q

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

A

Rh immune globulin (RhIG) protects D-negative mothers against production of anti-D.

80
Q

When should a mother receive Rh immune globulin (RhIG) if the baby is Rh+?

A

If the baby is Rh+, the mother must receive RhIG within 24-72 hours.

81
Q

What is the recommended blood type given to Rh-negative individuals?

A

Rh-negative individuals should receive Rh-negative blood.

82
Q

When is the initial administration of Rh immune globulin (RhIG) to Rh-negative moms?

A

RhIG is initially given to Rh-negative mothers at 28 weeks gestation.

83
Q

What do superscripts refer to in genetics?

A

Superscripts (Rh1) refer to genes inherited from both parents.

84
Q

What do subscripts refer to in genetics?

A

Subscripts (Rh1) refer to the agglutinogen (complex of antigens) inherited from both parents.

85
Q

How is the Rh1 gene expressed in shorthand notation?

A

The Rh1 gene codes for the Rh1 agglutinogen made of D, C, and e, which is usually written as DCe (leaving out the ‘h’).

86
Q

What are the characteristics of Rh antigens?

A

Rh antigens are proteins of 417 amino acids that cross the red cell membrane 12 times, with only small loops on the exterior.

87
Q

What is the Rosenfield system used for?

A

The Rosenfield system is used for computer data entry without making genetic assumptions in the Rh system.

88
Q

How are antigens designated in the Rh system?

A

Antigens are designated by numbers, for example: Rh1 = D, Rh2 = C, Rh3 = E, Rh4 = c, Rh5= e.

89
Q

What does the ISBT organization do?

A

The ISBT is an international organization that standardizes blood group system nomenclature by assigning 6-digit numbers for each antigen.

90
Q

How are genotypes determined from phenotypes?

A

Genotypes are determined by statistical probability based on the phenotype and gene frequency in a population.

91
Q

How can the most probable genotype be determined?

A

Once the phenotype is known, the most probable genotype can be determined based on the most common genotypes.

92
Q

What are the possible genotypes for Rh antigens D, C, c, E, and e?

A

Possible genotypes include homozygous and heterozygous combinations of the antigens.

93
Q

What should be done if testing results show D+ C+ c- E- e+?

A

If testing results show D+ C+ c- E- e+, start with D and determine if it’s positive or negative.

94
Q

If D is positive, what can be deduced about the individual’s genotype?

A

If D is positive, the individual is either homozygous or heterozygous for D, but it cannot be determined from these results alone.

95
Q

What should be done if C is negative?

A

If C is negative, put c on each chromosome.

96
Q

How can the homozygosity or heterozygosity of C be determined?

A

If C is positive and there is no c present, it is homozygous. If both C and c are present, it is heterozygous.

97
Q

What can cause interference with all cells reacting?

A

Cold agglutinin

98
Q

What is the most common cause of false positive anti-D testing?

A

Spontaneous agglutination when red cells are DAT positive

99
Q

When should you re-type a patient with low-protein reagents?

A

If using high-protein reagents and both the patient and the Rh control are positive

100
Q

What may cause false-positive Rh results?

A

Rouleaux caused by the presence of abnormal proteins in patient serum

101
Q

What should you do to resolve false-positive Rh results caused by rouleaux?

A

Wash cells in saline and re-test

102
Q

What can lead to false-positive reactions in blood bank testing?

A

Reagent contamination or bacterial contamination of reagents

103
Q

What can lead to false-positive Rh typing?

A

Antibody to a low incidence antigen

104
Q

What should you do if there is unidentified antibody to a low incidence antigen?

A

Test with another manufacturer’s reagent

105
Q

What can cause false-negative results in blood bank testing?

A

Incorrect cell suspension or incorrect cell to serum ratio

106
Q

What can result in the dispersal of weak D agglutination?

A

Overly vigorous re-suspension after centrifugation

107
Q

What can result in the destruction of antibody in reagents?

A

Prolonged or incorrect storage of reagents

108
Q

What may not react with weakened forms of an antigen?

A

Specific antibody that does not bind complement

109
Q

What is the most common class of Rh antibodies?

A

IgG

110
Q

When do Rh antibodies usually appear after exposure to Rh antigens?

A

Within 6 weeks to 6 months

111
Q

What type of media is best for demonstrating Rh antibodies?

A

High protein media or IAT

112
Q

What temperature is best for incubating Rh antibodies?

A

37°C to mimic in vivo conditions

113
Q

What enhances the reaction of Rh antibodies?

A

Testing against enzyme-treated RBCs

114
Q

Why do Rh antibodies not bind complement?

A

Rh antigens are too far apart on the RBC to allow two antibodies to bind close enough together

115
Q

When should anti-serum be added to the test?

A

Prior to the addition of cells

116
Q

What should be done if label is missing or unreadable on reagents?

A

Never use the reagents

117
Q

What should be done if wrong anti-serum is used?

A

Always read label to avoid the problem

118
Q

What is the result of hemolysis in extravascular Rh system antibodies?

A

The result of hemolysis in extravascular Rh system antibodies is picked off by phagocytic cells of the liver and spleen.

119
Q

How long does detectable antibody usually persist?

A

Detectable antibody usually persists for many years.

120
Q

What happens when antibody levels fall below detectable limits?

A

When antibody levels fall below detectable limits, a second exposure to the Rh system antigen will produce a rapid secondary immune response.

121
Q

What is the order of immunogenicity of Rh antibodies?

A

The order of immunogenicity of Rh antibodies is D > c > E > C > e.

122
Q

When should Rh typing be investigated?

A

Rh typing should be investigated when the Rh control test is positive or when results are weak or 1+ with commercial anti-D antiserum.

123
Q

What should be done if mixed field agglutination is suspected?

A

If mixed field agglutination is suspected, microscopic readings should ONLY be done.

124
Q

What should be done if an Rh typing discrepancy is found?

A

If an Rh typing discrepancy is found, the patient history should be reviewed and previous results must be compared to current results.

125
Q

What type of blood must be administered if a transfusion is required before resolution of an Rh typing problem?

A

Rh negative blood MUST be administered until the Rh typing problem is resolved.

126
Q

What may be the cause of false positive reactions with anti-D?

A

False positive reactions with anti-D may be due to the presence of antibodies to antigens of low frequency in the antiserum.

127
Q

What is recommended for all Rh testing?

A

Rh control is recommended for all Rh testing, especially for an AB individual.

128
Q

When should a DAT be performed as a control?

A

A DAT should be performed as a control for selected samples, such as cord, neonatal, samples demonstrating autoagglutination, to rule out false negative Rh typing due to blocked antigens.

129
Q

What should be done if there is doubt about the identity or specimen quality?

A

If there is doubt about the identity or specimen quality, a new specimen should be collected and re-tested.

130
Q

What may have caused a discrepancy if it has been resolved?

A

If a discrepancy has been resolved, it may have been caused by a procedural error, anti-sera not added, incorrect anti-sera used, a too strong cell suspension, excessive or insufficient centrifugation, tubes shaken too vigorously with weak agglutinates dispersed, or failure to re-suspend the entire cell button from the bottom of the tube.

131
Q

What are some possible causes of mixed field agglutination?

A

Some possible causes of mixed field agglutination include recent transfusion with different Rh donor units, contaminated specimen, or an unusual Rh phenotype.

132
Q

When is it not necessary to transfuse recipients with Rh Negative blood?

A

When they type as Rh Negative by direct methodology.

133
Q

What are the different types of Rh ANTISERA?

A

They may be low protein, high protein, saline based, chemically modified, monoclonal, or blends of monoclonals.

134
Q

Which Rh typing reagent was the first available and cannot be used for weak D testing?

A

Saline reagents, which contain IgM immunoglobulin.

135
Q

Why can’t saline anti-D be used to test cells coated with IgG antibodies?

A

It is low protein based and cannot be used to test cells coated with IgG antibodies, such as in weak D testing.

136
Q

What can cause FALSE POSITIVE Rh TYPING?

A

Spontaneous agglutination of DAT positive cells, immunoglobulins on the surface of red cells, presence of cold agglutinin, reagent contamination, presence of unidentified antibody to a low incidence antigen, failure to follow manufacturer’s instructions, or adding wrong reagent to test.

137
Q

What can cause FALSE NEGATIVE Rh TYPING?

A

Red cell suspension too heavy, failure to add antisera, incorrect antisera added, failure to follow manufacturer’s instructions, deterioration of anti-D antisera, inappropriate technique, resuspension of cell button done too vigorously, failure of anti-sera to react with variant antigen, or anti-sera in which the antibody is directed against a compound antigen.

138
Q

What are LOW PROTEIN REAGENTS?

A

They are the most recent Rh reagents introduced, including monoclonal antibodies derived from human/murine sources, suitable for different methods, and contain IgM or IgG monoclonal antibody for Rh control and weak D testing.

139
Q

What are the components of SLIDE AND MODIFIED TUBE ANTI-D?

A

IgG anti-D in protein concentration of 22-30%, mainly albumin, but other potentiators may be present.

140
Q

Why is Rh control essential for Rh(D) typing tests?

A

The Rh control is essential because it contains everything present in the anti-D typing sera except the anti-D, ensuring accurate testing.

141
Q

What determines if a genotype is homozygous or heterozygous?

A

The presence or absence of the same allele on both chromosomes determines if a genotype is homozygous or heterozygous.

142
Q

What is the more common genotype: DCe/dCe or DcE?

A

DCe/dCe is more common than DcE.

143
Q

What is the genotype if someone has D+, C+, c-, E-, and e+ antigens?

A

The genotype is D+ C+ c- E- e+.

144
Q

What can phenotyping be used for?

A

Phenotyping can be used for parentage testing, predicting HDFN, and confirming Rh antibody specificity.

145
Q

What is the protocol for Rh phenotyping?

A

The unknown RBCs are mixed with Rh antisera, and agglutination indicates the presence of the antigen on the cell, determining the phenotype.

146
Q

Why is molecular testing becoming more popular for blood group genes?

A

Molecular testing is used when anti-sera is not available for some antigens, and it can differentiate recently transfused individuals.

147
Q

What is Tippett’s theory regarding the RHD and RHCE genes?

A

Tippett’s theory states there are two closely-linked genes: RHD determines the presence of the D antigen, and RHCE determines the production of C, c, E, and e antigens.

148
Q

How many Rh genes do D positive people inherit from at least one parent?

A

D positive people inherit 2 Rh genes from at least one parent.

149
Q

What are the presumptive and most probable genotype frequencies listed as?

A

The textbook lists the genotype frequencies as ‘presumptive’ or ‘most probable’.

150
Q

What process are paternity testing of blood group Ag’s based on?

A

Paternity testing of blood group Ag’s is based on a process of exclusion.

151
Q

How many alleles can be inherited at the LW locus?

A

Three alleles can be inherited at the LW locus.

152
Q

Which allele is the most common at the LW locus?

A

LWa is the most common allele at the LW locus.

153
Q

Which allele is much less common at the LW locus?

A

LWb is much less common at the LW locus.

154
Q

What does the LW allele code for?

A

The LW allele codes for NO LW antigen.

155
Q

What is the genetic nature of LWa and LWb alleles?

A

LWa and LWb alleles are co-dominant.

156
Q

What is the genetic nature of the LW allele?

A

The LW allele is recessive.

157
Q

Where does LW negative occur?

A

LW negative occurs in all Rh null people.

158
Q

What do the CDE antigens require for LW antigens?

A

CDE antigens are required for LW antigens.

159
Q

How often is Anti-LW seen in laboratories?

A

Anti-LW is rarely seen in laboratories.

160
Q

When should the investigation of mosaic D consider anti-LW?

A

The investigation of mosaic D should consider anti-LW when a D positive patient appears to have formed anti-D.

161
Q

Which blood cells does LW antigen react more strongly with?

A

LW antigen reacts more strongly with D positive blood cells than with D negative blood cells.

162
Q

What are some causes of positive Rh Control?

A

Rouleaux when unwashed cells used, Strong autoagglutinins, Positive DAT.

163
Q

What are some causes of negative Rh Control?

A

Excessive feto-maternal bleed, Dual red cell population due to bone marrow transplant, Genetic anomalies.

164
Q

What are Rh deletion phenotypes and how do they affect antigen expression?

A

Rh deletion phenotypes occur when pieces of the genetic material representing CE antigen are deleted. They enhance expression of D antigen and lack alleles at the Ee locus or Ee and Cc loci.

165
Q

How are Rhnull individuals characterized?

A

Rhnull individuals have no Rh antigens (D, C, c, E, e) detectable on their red cells. They can transmit normal Rh antigens to their offspring.

166
Q

What is the common type of Rhnull phenotype?

A

The common type of Rhnull phenotype has the core Rh polypeptide missing.

167
Q

What is the less common type of Rhnull phenotype?

A

The less common type of Rhnull phenotype has the regulator gene that turns off the expression of Rh missing.

168
Q

What is the impact of Rhnull phenotype on other blood group antigens?

A

Rhnull individuals are also negative for antigens like S’s, U, and LW due to their absence of Rh antigens.

169
Q

What are the characteristics of Rhmod phenotype?

A

Rhmod phenotype is similar to Rhnull phenotype, but the Rh antigens are present in greatly reduced amounts due to a mutation of the RHAG gene.

170
Q

What is the immune antibody Anti-Rh29?

A

Anti-Rh29 is the immune antibody made by rare people of the Rhnull type. It is usually potent and may cause transfusion reactions or hemolytic disease of the newborn.

171
Q

What is the serological significance of LW antigens?

A

LW antigens are serologically similar to Rh, and they react strongly with D positive cells and weakly with D negative cells.

172
Q

When should RhIG be administered to Rh Negative women?

A

Within 72 hours of delivering an Rh Positive baby

173
Q

What is the purpose of RhIG?

A

To prevent the formation of permanent anti-D antibody

174
Q

Why is anti-D injected passively?

A

To bind to any Rh Pos cells from the fetus

175
Q

How is weak D expression identified?

A

Through weakly expressed D antigen after incubation and antiglobulin testing

176
Q

What are the three ways weak D occurs?

A

Positional, Mosaic, Genetic

177
Q

What is the weak D Du phenotype?

A

Weakly expressed D antigen seen as agglutination that easily breaks apart

178
Q

Which population is weak D more common in?

A

Blacks

179
Q

Can weak D testing be performed using Gel methodology?

A

No

180
Q

When should RhIG be administered to Rh Negative women?

A

Within 72 hours of delivering an Rh Positive baby

181
Q

Which genetic variation causes weak D?

A

Quantitative variation of D gene

182
Q

What antigens are usually found together with anti-C?

A

C, e, E

183
Q

Which Rh antigen is found on cells carrying the D antigen?

A

G

184
Q

What are the low incidence Rh antigens?

A

Cw, V, VS, Rh32, Rh33

185
Q

What type of antibodies are usually made by exposure to Rh antigens?

A

IgG

186
Q

How are Rh antibodies detected?

A

Through the IAT (Indirect Antiglobulin Test)

187
Q

What is the importance of checking patient history for Rh antibodies?

A

To determine if a rapid secondary response may occur upon re-exposure to the antigen

188
Q

How can false positive results be enhanced in Rh antibody testing?

A

High protein, low ionic strength solution, enzymes, or polyethylene glycol

189
Q

What can antibodies to the Rh system cause?

A

Hemolytic transfusion reactions

190
Q

What should be done if the Rh control is positive?

A

Perform a DAT (Direct Antiglobulin Test) to determine if uptake of alloantibody or autoantibody is causing the positive Rh Control

191
Q

What should be done if the Rh cannot be determined and transfusion is required?

A

Transfuse Rh Negative blood

transfusion (7 decks)

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