BB - Day 1 Flashcards

1
Q

Washing cells is important before using this particular reagent. What does the washing step remove?

A

Antihuman globulin (AHG) reagent

Unbound IgG and other free globulin molecules/proteins that create false reactions
-AHG binds to bound IgG, causes agglutination

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2
Q

What does the DAT test demonstrate? What reagent is used to check for this?

A

In-vivo coating of RBCs with globulins (IgG and/or C3)

AHG - binds to IgG or C3, which are bound to RBCs, causing agglutination
-detects in vivo hemolysis

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3
Q

Why is AHG needed to agglutinate RBCs?

A

IgG and C3 are so small, they cannot agglutinate RBCs by themselves
-AHG binds to IgG or C3, which are bound to RBCs

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4
Q

When check cells are added to a negative tube, assuming the tube really is negative, what kind of reaction grade should we expect? What happens if this does not happen?

A

2+ agglutination = true negative (1+ for DAT)

Repeat test

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5
Q

True/False - both negative and positive reactions should be tested with check cells

A

False

  • only negative reactions should be tested
  • positive reaction means washing step and AHG binding worked, so no need to waste reagent
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6
Q

DAT positive and DAT negative test results - what is the agglutination result and check cell result?

A

DAT positive = agglutination in test tube, no check cell needed

DAT negative = no agglutination in test tube, check cells agglutination

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7
Q

Incompatible ABO donor blood type mixing with patient blood causes what kind of hemolysis?

A

Intravascular hemolysis

  • ABO are IgM antibodies
  • triggers complement cascade
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8
Q

An Rh-positive cell has this antigen on its surface…

A

D antigen

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9
Q

Anti-D made in an Rh negative mother can cause HDFN in an Rh ___ child

A

Positive

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10
Q

Difference between forward type and reverse type. Which test is the confirmatory test?

A

Forward type looks for A, B, or AB antigens on patient’s RBCs

Reverse type looks for anti-A, anti-B, or anti-A,B antibodies in patient’s serum
-aka “backtype”

Reverse type is the confirmation of the forward type

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11
Q

Which antibodies are “naturally-occurring” antibodies? What immunoglobulin class(es) are they predominantly?

A

anti-A and anti-B = predominantly IgM

  • called saline reactive antibodies because they do not need a high protein medium to react
  • react at room temperature or lower

anti-A,B = predominantly IgG

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12
Q

Which of the following antibodies are saline reactive and which are protein reactive: anti-D, anti-A, anti-B, anti-A,B. Which are IgM and which are IgG

A

anti-A, anti-B, anti-A,B = saline-reactive
anti-D = protein-reactive

anti-A, anti-B = IgM
anti-A,B, anti-D = IgG

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13
Q

The weak D test is performed on tubes with these results…

A

Tubes that are negative for anti-D and Rh control

-some cells express D antigen so weakly they do not agglutinate with most anti-D reagents

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14
Q

What is done in a weak D test to enhance agglutination?

A

Incubation (15 mins at 37C)

Followed by addition of AHG

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15
Q

Weak D is an example of a direct or indirect agglutination test?

A

Indirect - cells sensitized in vitro at 37C with antiserum before antiglobulin testing

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16
Q

Which class of antibodies can across the placenta? Which region of the antibody is required to aid in the transport?

A

IgG

Fc

17
Q

Most clinically significant class of antibodies

A

IgG

-some IgM also clinically significant (ABO), but mostly it’s IgG

18
Q

Pentameric IgM are joined together by the…

A

J chain

  • covalent bonds can be cleaved to detect IgG
  • IgM removed with beta-mercaptoethanol or DTT
19
Q

This blood group system makes antigens in tissue that eventually find their way onto RBCs. Is the blood group system clinically significant?

A

Lewis blood group system

No

20
Q

Binding of RBC antibodies to complement causes…

A

Intravascular hemolysis

  • caused by IgG antibodies
  • exception: paroxysmal cold hemoglobinuria (PCH) caused by IgM
21
Q

Extravascular hemolysis happens in the… Due to…

A

Spleen, liver

RBCs coated with antibodies are removed by macrophages

22
Q

Which red blood cell antigen is the most immunogenic?

A

D antigen

-70% of D-negative people will be sensitized if exposed to D antigen

23
Q

Kell blood group system - is it clinically significant? Which antigen is the most immunogenic after the D antigen?

A

Yes
-IgG

K

24
Q

If you naturally make an RBC antigen, do you also make the antibody against it?

A

No

-autoimmunity if this happens

25
Q

This blood group system is notorious for falling below detectable limits. Is it clinically significant?

A

Kidd
-IgG

Yes

26
Q

The most important step before starting any new test is to know…

A

Patient’s history

27
Q

DAT vs IAT - which is in vitro and which is in vivo? Both tests use this reagent to bind to antibodies to help RBCs agglutinate…

A

DAT = in vivo
-detects antibodies bound to RBCs

IAT = in vitro

  • HDFN, weak D
  • take patient’s serum and add test RBCs

AHG = Coombs reagents

28
Q

Factors influencing agglutination reactions (6)

A

22% albumin

LISS

PeG

Proteolytic enzymes – ficin (fig), papain (papaya), trypsin (pig stomach), bromelin (pineapple)

Chemical reduction – DTT, B-2-ME – thiol reducing agents

ZZAP – thiol reducing + proteolytic enzyme – causes dissociation of IgG molecule from the RBC surface and alters the surface antigen

29
Q

Monospecific AHG detects… Polyspecific AHG detects…

A

IgG

IgG and complement (C3)

30
Q

Monospecific AHG targets this particular region of the antibody…

A

Fc heavy chain region

31
Q

A DAT is performed when we suspect a patient is having ___. Two cases when we would perform a DAT…

A

Hemolysis
-due to antibodies binding to RBCs, causing intra/extravascular hemolysis

Transfusion reaction, newborns (HDFN)

32
Q

What are check cells

A

Sensitized cells that will agglutinate unbound AHG remaining in a negative test tube

  • AHG did not/could not bind to Fc of antibody on test RBC, so free in solution to bind to check cells
  • only use for negative tubes
33
Q

Rouleaux formation in the blood usually indicates too much… How do we get rid of it?

A

Protein (ie multiple myeloma)

More washes

34
Q

If DAT is positive, what is the auto-control result?

A

Positive
-remember that DAT checks for hemolysis. Auto-control uses patient’s RBCs plus serum containing the antibodies that target antigens on these RBCs

35
Q

When grading RBC agglutination, the point at which the background looks turbid with tiny agglutinates is graded as…

A

1+

At 2+, the background is clear