BB Unit 2 Quiz Questions

Incubating a specimen below room temperature (e.g., at 4 C) is a technique used to:

Enhance weak or unexpected cold alloantibody reactions to aid in identification

Which of the following corrective actions can help avoid detecting a clinically insignificant cold alloantibody during routine antibody screening?

 

Omitting the immediate-spin and 37 C phase readings, reading only the AHG phase

Secondary, chronic Cold Agglutinin Syndrome (CAS) is most classically associated with which patient population?

 

Elderly patients with lymphoma, chronic lymphocytic leukemia (CLL), or Waldenstrom macroglobulinemia

Cold autoantibodies typically produce a positive DAT due to which mechanism?

 

Complement (C3) deposition on the red cell surface after the IgM autoantibody has dissociated

A cold autoantibody screen/panel is most useful for which of the following purposes?

 

Confirming the presence of a cold autoantibody and helping identify its specificity (if applicable) before pursuing further identification or avoidance techniques

Cold alloantibodies are most typically characterized by which immunoglobulin class and reactivity pattern?

 

IgM, reactive at immediate spin and sometimes at 37 C

. In PCH, full complement activation and hemolysis occur under which condition?

 

Only after the antibody-coated red cells are warmed back to 37 C

Which clinical symptom of Cold Agglutinin Syndrome (CAS) is most directly caused by cold-induced agglutination in the peripheral extremities?

 

Raynaud's phenomenon (including acrocyanosis, numbness, and pain)

Rabbit erythrocyte stroma (RESt) is useful for adsorbing cold autoantibodies, but has which important limitation?

 

 

It cannot be used for reverse grouping or crossmatch, since RESt carries B-like antigens and may also adsorb anti-Vel and other clinically significant IgM antibodies

Autoimmune hemolytic anemia (AIHA) is classified into which of the following categories based on antibody type?

 

Cold AIHA (IgM), warm AIHA (IgG), mixed-type (IgM + IgG), and PCH (IgG biphasic hemolysin)

Anti-I is considered the most commonly encountered cold autoantibody. Which finding on a cold panel would be most consistent with anti-I specificity?

 

Reactivity with all adult screening cells and the autocontrol, but no reactivity with cord blood cells

Autoantibodies are generally distinguished from alloantibodies by which serologic characteristic?

 Autoantibodies react with the patient's own (autologous) red cells in addition to donor and reagent cells

Which of the following is a recommended corrective action to avoid cold autoantibody interference during routine pretransfusion testing?

 

Using a monospecific anti-IgG AHG reagent rather than a polyspecific reagent

A nonpathogenic cold agglutinin, as commonly found in healthy adults, is best characterized by which of the following?

 

Polyclonal, low titer, and does not react above approximately 30 C

Paroxysmal Cold Hemoglobinuria (PCH) is caused by which type of antibody?

 A biphasic hemolysin (the Donath-Landsteiner antibody), an IgG with anti-P specificity

Which of the following is the most critical diagnostic task when an autoantibody is identified in a patient's plasma?

 

Identifying whether a clinically significant alloantibody is also present, since it may be masked by the autoantibody

Autoanti-H, a benign cold autoantibody often found in A1 and A1B individuals, should not be confused with which of the following, despite reacting with a similar antigen?

 

The potent alloanti-H produced by individuals with the Bombay phenotype

A reaction persists through the AHG phase, and the MLS wants to determine whether this is due to a clinically insignificant cold antibody with an unusually wide thermal range, or a true, clinically significant IgG antibody. Which technique would best resolve this?

 

Treating the plasma with 0.01M DTT and comparing the treated result to a saline dilution control

A cold panel performed on a group A patient's plasma shows 1+ reactivity with both cord cells, 1+ reactivity with A1 cells, and 2+ reactivity with A2 cells, all at 4 C. What antibody specificity is most consistent with this pattern, and why does A2 react more strongly than A1?

 

Anti-HI; A2 cells express more H antigen than A1 cells, so a cold antibody reacting with both the H and I antigens shows stronger reactivity with A2

A neutralization study for suspected anti-Leb is performed. The control (plasma + saline) shows 0 reactivity, and the neutralized tube (plasma + Lewis substance) also shows 0 reactivity. What is the correct interpretation?

 

The antibody was likely already weak/diluted; true neutralization cannot be confirmed, and antibody specificity remains undetermined

In the immune complex mechanism, the drug loosely binds an RBC membrane protein, forming a drug-protein complex against which the patient produces IgG and/or IgM. What is a hallmark clinical feature of this mechanism?

The DAT is often positive for complement, and it can cause acute intravascular hemolysis; this mechanism is also drug-dependent

Which of the following is NOT a recognized cause of a positive DAT?

 

A first-time blood donation from a healthy, non-medicated volunteer donor

Explain the fundamental difference between testing a patient's plasma and testing a patient's eluate.

 

Plasma detects free-floating antibody not attached to red cells (via IAT), while an eluate is prepared to recover antibody that was actually bound to (coating) the patient's red cells

A patient's plasma (IAT) is negative, but the DAT is positive and the eluate is also negative. Which mechanism is most consistent with this pattern?

 

A drug-dependent mechanism, where reactivity requires the drug to be present in the test system

What is the purpose of testing the supernatant from the last (final) wash step before performing an elution, and what result should it show?

 

It is tested as a negative control; it must test negative to prove that eluate reactivity reflects antibody truly bound to the red cells rather than residual, incompletely washed plasma antibody

A patient's plasma (IAT), DAT, and eluate are all positive, with the eluate reacting against all panel cells tested (pan-reactive). What is the most likely cause?

 

True warm autoantibody (WAIHA)

A differential DAT is positive for both monospecific anti-IgG and monospecific anti-C3d. Which of the following is LEAST likely to explain this combined pattern?

 

Nonimmunologic protein adsorption from a drug

A differential DAT shows a positive result with monospecific anti-IgG and a negative result with monospecific anti-C3d. Which interpretation is most likely?

 

Warm autoantibody or a drug-induced mechanism

A patient's autocontrol and DAT are both positive. The patient was transfused two units of red blood cells four days ago. What important alternative explanation should be considered before concluding the patient has a true autoantibody?

 

The result may simply reflect transfused donor cells coated with an alloantibody the patient is actively producing, rather than a true autoantibody

Which elution technique lowers pH to cause antibody dissociation and uses organic solvents to dissolve the RBC lipid bilayer, and is the most commonly used method with reliable recovery of IgG alloantibodies?

 

Acid elution

How are drug-induced DAT mechanisms broadly classified based on whether the drug must be present during testing?

 

Drug-dependent mechanisms (the drug must be present in the test system) versus drug-independent mechanisms (the antibody behaves like a true autoantibody, with no drug needed in testing)

In the membrane modification (nonimmunologic protein adsorption, NIPA) mechanism, the drug alters the RBC membrane so that plasma proteins adsorb nonspecifically. What testing pattern results?

 

DAT positive; eluate typically nonreactive since no true antibody to the drug or red cell is produced

What is the fundamental difference in what the DAT and the IAT each detect?

The DAT detects antibody/complement already bound to red cells in vivo, while the IAT detects free antibody in plasma reacting with reagent cells in vitro

Why does a high-titer warm autoantibody frequently cause panagglutination on the antibody screen, panel, and crossmatched units?

 

The patient's red cells become saturated with autoantibody, and excess autoantibody circulates freely in the plasma, reacting with essentially all reagent and donor cells

Why might the false-positive DAT and panagglutination caused by IVIG be mistaken for a true warm autoantibody?

 

The serologic pattern looks identical to true WAIHA, so the patient's medication history (recent IVIG) is the key clue distinguishing the two

A DAT is positive for complement (C3d) only, with a negative anti-IgG result. Should an elution be performed? Explain.

 

No, because a C3d-only positive DAT implies an IgM antibody was bound in vivo and has already dissociated, leaving no IgG remaining to elute

A patient has a positive DAT, but the prepared eluate is nonreactive against a standard antibody identification panel composed of group O reagent cells. Which of the following is the most likely explanation, keeping in mind that standard panel cells lack A and B antigens?

The antibody present is an ABO antibody (e.g., anti-A or anti-B), which would not react against group O panel cells

A patient with an anti-e-like warm autoantibody (and who is e-positive) is transfused with e-negative units anyway. What is a potential disadvantage of this approach?

 

Since e-negative units are also E-positive, repeated transfusion of E-positive blood could induce a true allo-anti-E

A patient's autocontrol is positive, but the DAT is negative. What does this combination most likely indicate?

 

A technical or false-positive result in the autocontrol, rather than true antibody coating of the red cells, since the DAT directly tests washed cells

In the drug adsorption (hapten) mechanism, the drug binds tightly to the RBC membrane and the patient produces an anti-drug IgG antibody. What is the resulting testing pattern?

 

DAT positive; plasma and panel nonreactive unless the drug is added directly to the test system (drug-dependent)

A patient's plasma is positive by IAT and the DAT is positive, but the eluate is nonreactive against all cells tested. Which of the following best explains this pattern?

 

Nonimmunologic protein adsorption (NIPA) or a drug-related mechanism

Which drug-induced mechanism results in a positive DAT without a true antibody-antigen immune reaction, and instead involves the drug nonspecifically altering the red cell membrane so that plasma proteins adsorb onto it?

 

Membrane modification (nonimmunologic protein adsorption, NIPA)

What is the fundamental difference between testing a patient's plasma and testing a patient's eluate?

 

Plasma detects free antibody circulating in the patient's serum, while eluate detects antibody that was actually bound to the red cell membrane

In the drug adsorption mechanism of drug-induced immune hemolysis, what is the underlying process?

 

The drug binds covalently to the RBC membrane; anti-IgG antibody forms and binds to drug-coated cell, RBCs cleared my macrophages

An eluate reacts with only some of the panel cells tested (a partial reactivity pattern) rather than all cells. What does this most likely indicate?

 

An alloantibody with a specific antigen target

A patient's plasma is positive by IAT, the DAT is positive, and the eluate is panreactive against all screening/panel cells. What is the most likely interpretation?

 

True warm autoimmune hemolytic anemia (WAIHA)

A patient with a panreactive eluate types as e-antigen positive on their own red cells. Why does this finding argue against a true alloantibody specificity of anti-e?

 

Because anti-e can only be made by an e-negative individual reacting to foreign e-positive cells; a patient who is e-positive would not form a true allo-anti-e against their own antigen

DTT treatment of reagent red cells is used to resolve anti-CD38 (daratumumab) interference. What important limitation must be considered when selecting donor units for a patient on anti-CD38 therapy?

 

DTT also destroys Kell system antigens, so K-negative units are typically selected instead of relying on DTT-treated donor cells for Kell typing

Which elution method uses freeze-thaw cycling to disrupt the red cell membrane and release antibody, and is best suited for cold-reactive antibody investigations?

 

Lui freeze-thaw elution

What is the purpose of testing the last wash supernatant before performing an elution?

 

To serve as a quality control step, confirming that residual free antibody has been adequately removed before the eluate is prepared

A patient recently received IVIG (intravenous immunoglobulin) therapy. How can this affect DAT and eluate testing, potentially mimicking warm autoimmune hemolytic anemia?

 

IVIG can cause a false-positive DAT and a panreactive eluate due to passively transferred antibody coating the red cells

A patient taking a certain medication develops a positive DAT and an eluate that is panreactive, clinically and serologically indistinguishable from true warm autoimmune hemolytic anemia. Which drug-induced mechanism does this describe?

 

Autoantibody induction mechanism

 

A patient's DAT is positive with anti-IgG only (anti-C3d negative). Which of the following is the most likely cause?

 

Warm autoantibody or drug-induced antibody (immune mechanism)

When passive ABO antibody from IVIG or platelet transfusion is suspected as the cause of a positive eluate, why should the eluate also be tested against A1 and B reverse-grouping cells rather than only standard antibody panel cells?

 

Standard panel cells are all group O and would not reveal an ABO antibody, so A1 and B cells are needed to detect passively acquired anti-A or anti-B

What is the key difference between an autocontrol and a DAT?

 

The autocontrol tests patient cells against patient serum/plasma, while the DAT tests patient cells directly against AHG reagent to detect in vivo sensitization

Anti-CD38 therapy (e.g., daratumumab) is known to interfere with pretransfusion testing. What is the nature of this interference, and how is it typically resolved?

 

It causes panagglutination on antibody screens and panels because CD38 is expressed on reagent red cells; this can be resolved by treating reagent cells with DTT to destroy CD38

A patient's DAT shows anti-C3d reactivity only, with a negative anti-IgG. Why is performing an elution NOT indicated in this case?

 

There is no IgG bound to the red cell membrane to elute, since only complement is present

A patient presents with panagglutination on the antibody screen, a positive DAT, and a panreactive eluate. What is the primary goal of further pretransfusion workup in this scenario?

 

Rule out an underlying alloantibody that may be masked by the autoantibody

Which drug-induced mechanism is characterized by antibody-drug immune complexes attaching loosely to the red cell membrane and often fixing complement, typically detected by a positive anti-C3d DAT?

 

Immune complex mechanism

A DAT performed with polyspecific AHG is positive. Both anti-IgG and anti-C3d monospecific reagents are also positive. Which of the following is most consistent with this pattern?

 

Warm autoantibody with complement activation, mixed-type AIHA, or a delayed hemolytic transfusion reaction