3 Rh BLOOD GROUP SYSTEM

Question 1

(1) A complete Rh typing for antigens C, c, D, E, and e revealed negative results for C, D, and E. How is the individual designated?

A. Rh positive
B. Rh negative
C. Positive for c and e
D. Impossible to determine

Answer 1

B. Rh negative

Rh positive refers to the presence of D antigen; Rh negative refers to the absence of D antigen. These designations are for D antigen only and do not involve other Rh antigens.

Question 2

(2) How is an individual with genotype Dce/dce classified?

A. Rh positive
B. Rh negative
C. Rhnull
D. Total Rh

Answer 2

A. Rh positive

This individual has D antigen and is classified as Rh positive. Any genotype containing D antigen will be considered Rh positive.

Question 3

(3) If a patient has a positive DAT, should you perform a weak D test on the cells?

A. No, the cells are already coated with antibody
B. No, the cells are Rhnull
C. Yes, the immunoglobulin will not interfere with the test
D. Yes, Rh reagents are enhanced in protein media

Answer 3

A. No, the cells are already coated with antibody

If a person has a positive DAT, the RBCs are coated with immunoglobulin. If a test for weak D were performed, the test would yield positive results independent of the presence or absence of D antigen on the RBCs.

Question 4

(4) Which donor unit is selected for a recipient with anti-c?

A. r´r
B. R0R1
C. R2r´
D. r´ry

Answer 4

D. r´ry

The designation r’ is dCe and ry is dCE, neither of which contains c antigen. The other three Rh types contain c antigen and could not be used in transfusion for a person with anti-c.

Question 5

(5) Which genotype usually shows the strongest reaction with anti-D?

A. DCE/DCE
B. Dce/dCe
C. D–/D–
D. –CE/–ce

Answer 5

C. D–/D–

The phenotype that results from D–/D– is classified as enhanced D because it shows a stronger reaction than expected with anti-D. Such cells have a greater amount of D antigen than normal. This is thought to result from a larger quantity of precursors being available to the D genes because there is no competition from other Rh genes.

Question 6

(6) Why is testing for Rh antigens and antibodies different from ABO testing?

A. ABO reactions are primarily caused by IgM antibodies and usually occur at room temperature; Rh antibodies are IgG and agglutination usually requires a 37°C incubation and enhancement media
B. ABO antigens are attached to receptors on the outside of the RBC and do not require any special enhancement for testing; Rh antigens are loosely attached to the RBC membrane and require enhancement for detection
C. Both ABO and Rh antigens and antibodies have similar structures, but Rh antibodies are configured so that special techniques are needed to facilitate binding to Rh antigens
D. There is no difference in ABO and Rh testing; both may be conducted at room temperature with no special enhancement needed for reaction

Answer 6

A. ABO reactions are primarily caused by IgM antibodies and usually occur at room temperature; Rh antibodies are IgG and agglutination usually requires a 37°C incubation and enhancement media

Detection of ABO and Rh antigens and antibodies requires different reaction conditions. ABO antibodies are naturally occurring IgM molecules and react best at room temperature. Rh antibodies are generally immune IgG molecules that result from transfusion or pregnancy. Detection may require 37°C incubation and/or enhancement techniques.

Question 7

(7) Testing reveals a weak D that reacts 1+ after indirect antiglobulin testing (IAT). How is this result classified?

A. Rh-positive
B. Rh-negative, Du positive
C. Rh-negative
D. Rh-positive, Du positive

Answer 7

A. Rh-positive

Blood tested for weak D that shows 1+ reaction after IAT is classified as Rh positive. The weak D designation is not noted in the reporting of the result.

Question 8

(8) What is one possible genotype for a patient who develops anti-C antibody?

A. R1r
B. R1R1
C. r’r
D. rr

Answer 8

D. rr

Only rr (dce/dce) does not contain C antigen. A person will form alloantibodies only to the antigens he or she lacks.

Question 9

(9) A patient developed a combination of Rh antibodies: anti-C, anti-E, and anti-D. Can compatible blood be found for this patient?

A. It is almost impossible to find blood lacking C, E, and D antigens
B. rr blood could be used without causing a problem
C. R0R0 may be used because it lacks all three antigens
D. Although rare, ryr blood may be obtained from close relatives of the patient

Answer 9

B. rr blood could be used without causing a problem

The genotype rr (dce/dce) lacks D, C, and E antigens and would be suitable for an individual who has developed antibodies to all three antigens. This is the most common Rh-negative genotype and is found in nearly 14% of blood donors who are white.

Question 10

(10) 10. A patient tests positive for weak D but also appears to have anti-D in his serum. What may be the problem?

A. Mixup of samples or testing error
B. Most weak D individuals make anti-D
C. The problem could be caused by a disease state
D. A D mosaic may make antibodies to missing antigen parts

Answer 10

D. A D mosaic may make antibodies to missing antigen parts

The D antigen comprises different parts designated as a mosaic. If an individual lacks parts of the antigen, he or she may make antibodies to the missing parts if exposed to the whole D antigen.

Question 11

(11) Which offspring is not possible from a mother who is R1R2 and a father who is R1r?

A. DcE/DcE
B. Dce/DCe
C. DcE/DCe
D. Dce/dce

Answer 11

A. DcE/DcE

DcE/DcE (R2R2) is not possible because R2 can be inherited only from the mother and is not present in the father.

Question 12

(12) Which weak D phenotypes necessitate Rh immune globulin (RhIg) prophylaxis?

A. 1
B. 2
C. 3
D. None of the above

Answer 12

D. None of the above

Weak D phenotypes 1, 2, and 3 (as well as 4) are not associated with formation of anti-D negating RhIg prophylaxis. Weak D phenotypes 5, 11, 15, 19, and 20 would require RhIg prophylaxis.

Question 13

(13) What antibodies could an R1R1 make if exposed to R2R2 blood?

A. Anti-e and anti-C
B. Anti-E and anti-c
C. Anti-E and anti-C
D. Anti-e and anti-c

Answer 13

B. Anti-E and anti-c

The R1R1 (DCe/DCe) individual does not have the E or c antigen, and could make anti-E and anti-c antibodies when exposed to R2R2 cells (DcE/DcE).

Question 14

(14) What does the genotype —/— represent in the Rh system?

A. Rh negative
B. D mosaic
C. Rh null
D. Total Rh

Answer 14

C. Rh null

A person who is Rhnull shows no Rh antigens on his or her RBCs. Loss of Rh antigens is very unlikely to happen because Rh antigens are integral parts of the RBC membrane. The Rhnull phenotype can result from either genetic suppression of the Rh genes or inheritance of amorphic genes at the Rh locus.

Question 15

(15) What techniques are necessary for weak D testing?

A. Saline + 22°C incubation
B. Albumin or LISS + 37°C incubation
C. Saline + 37°C incubation
D. 37°C incubation + IAT

Answer 15

D. 37°C incubation + IAT

Weak D testing requires both 37°C incubation and the IAT procedure. Anti-D is an IgG antibody, and attachment of the D antigen is optimized at warmer temperatures. AHG in the IAT phase facilitates lattice formation by binding to the antigen–antibody complexes.

Question 16

(16) A patient types as AB and appears to be Rh positive on slide typing. What additional tests should be performed for tube typing?

A. Rh negative control
B. Direct antiglobulin test
C. Low-protein Rh antisera
D. No additional testing is needed

Answer 16

A. Rh negative control

An Rh-negative control (patient cells in saline or 6% albumin) should be run if a sample appears to be AB positive. The ABO test serves as the Rh control for other ABO types.

Question 17

(17) According to the Wiener nomenclature and/or genetic theory of Rh inheritance:

A. There are three closely linked loci, each with a primary set of allelic genes
B. The alleles are named R1, R2, R0, r, r’, r”, Rz, and ry
C. There are multiple alleles at a single complex locus that determine each Rh antigen
D. The antigens are named D, C, E, c, and e

Answer 17

C. There are multiple alleles at a single complex locus that determine each Rh antigen

Wiener proposed a single-locus theory for Rh, with multiple alleles determining surface molecules that embody numerous antigens.

Question 18

(18) The Wiener nomenclature for the E antigen is:

A. hr’
B. hrv’
C. rh”
D. Rh0

Answer 18

C. rh”

The Wiener designation for the E antigen is rh”. The Wiener designation hr’ denotes c, hr” denotes e, and Rh0 is D.

Question 19

(19) A physician orders 2 units of leukocyte-reduced RBCs. The patient is a 55-year-old male with anemia. He types as an AB negative, and his antibody screen is negative. There is only 1 unit of AB negative in inventory. What is the next blood type that should be given?

A. AB positive (patient is male)
B. A negative
C. B negative
D. O negative

Answer 19

B. A negative

Although giving Rh-positive RBCs to an Rh-negative patient would not harm the patient in this case, because he is male, giving A negative would be the first choice. You should not expose a patient to the D antigen, if possible, and the residual anti-B in a unit of A-negative packed cells is less immunogenic than giving B or O RBCs.

Question 20

(20) Which technology may report an Rh-weak D positive as Rh negative?

A. Gel system
B. Solid phase
C. Tube testing
D. None of these options

Answer 20

A. Gel system

The Gel system cannot detect a weak D phenotype because there is no washing phase in the Gel system.