A 40-year-old woman with warm AIHA has a hemoglobin of 62 g/L (6.2 g/dL), is stable, and needs transfusion. Every crossmatched unit reacts 2+ at the antiglobulin phase, and the resident asks for the least incompatible unit. What is the best response?

Exclude alloantibodies by adsorption, then give matched units

Withhold transfusion until the DAT becomes negative

Issue D-negative units, which the autoantibody cannot bind

Issue the weakest-reacting unit, as it will survive longest

A blood sample is sent for a cold agglutinin titer. How should it be handled before the serum is separated?

Kept at 37 °C until the serum is separated

Refrigerated at 4 °C straight after collection

Frozen whole at −20 °C before testing

Left at room temperature for 2 hours

A patient on piperacillin-tazobactam has a positive DAT with anti-IgG and anti-C3 but no hemolysis, and the eluate is nonreactive. Red cells treated with tazobactam alone react with the patient's plasma and also with plasma from several healthy donors. These findings point to:

Nonimmunologic protein adsorption onto the cells

A drug-independent warm autoantibody

A drug-dependent antibody acting with drug in solution

Drug adsorption with an IgG antibody to the drug

Two patients have anti-I. Patient 1: titer 2,048 at 4 °C, no reactivity above 20 °C. Patient 2: titer 128 at 4 °C, reacting at 30 °C in albumin. Which patient is more likely to have hemolysis, and why?

Patient 2, as the antibody reacts near body temperature

Neither, as anti-I does not cause hemolysis

Both equally, as both antibodies are anti-I

Patient 1, as the titer at 4 °C is much higher

Immune hemolytic anemias in the blood bank

9 DOH Abu Dhabi (HAAD) lab licensing practice questions on Immune hemolytic anemias in the blood bank, part of Blood Banking. The first 9 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A 40-year-old woman with warm AIHA has a hemoglobin of 62 g/L (6.2 g/dL), is stable, and needs transfusion. Every crossmatched unit reacts 2+ at the antiglobulin phase, and the resident asks for the least incompatible unit. What is the best response?
1. AWithhold transfusion until the DAT becomes negative
2. BIssue D-negative units, which the autoantibody cannot bind
3. CExclude alloantibodies by adsorption, then give matched units
4. DIssue the weakest-reacting unit, as it will survive longest
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Answer: C · Exclude alloantibodies by adsorption, then give matched units
In warm AIHA the autoantibody reacts with nearly all red cells, so every crossmatch is incompatible and differences in strength say little about survival. The real danger is a hidden alloantibody, which is found in a sizeable share of patients who have been transfused or pregnant. Autoadsorption (if the patient has not been transfused in the last 3 months) or allogeneic adsorption removes the autoantibody so that alloantibodies can be identified, and units lacking those antigens, often phenotype-matched, are given. Transfusion should not be withheld when it is clinically needed.
- A: The DAT can stay positive for months, and needed blood should not be withheld.
- B: Warm autoantibodies usually react with D-negative cells as well.
- D: Reaction strength reflects the autoantibody and does not predict survival in vivo.
Question 2 · Easy
A blood sample is sent for a cold agglutinin titer. How should it be handled before the serum is separated?
1. ARefrigerated at 4 °C straight after collection
2. BFrozen whole at −20 °C before testing
3. CLeft at room temperature for 2 hours
4. DKept at 37 °C until the serum is separated
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Answer: D · Kept at 37 °C until the serum is separated
A cold autoantibody binds the patient's own red cells as the sample cools. If the sample clots or is stored cold, the antibody stays on the cells and the titer measured in the serum is falsely low. The tube is kept at 37 °C, for example in a heat block or warm water bath, until the serum is separated from the cells. The same care is used when strong cold agglutinins interfere with ABO grouping.
- A: Refrigeration lets the antibody bind the patient's cells, so the titer is falsely low.
- B: Freezing whole blood lyses the cells and does not stop the antibody binding first.
- C: Cooling to room temperature also lets the antibody bind the cells.
Question 3 · Hard
A patient on piperacillin-tazobactam has a positive DAT with anti-IgG and anti-C3 but no hemolysis, and the eluate is nonreactive. Red cells treated with tazobactam alone react with the patient's plasma and also with plasma from several healthy donors. These findings point to:
1. AA drug-independent warm autoantibody
2. BA drug-dependent antibody acting with drug in solution
3. CDrug adsorption with an IgG antibody to the drug
4. DNonimmunologic protein adsorption onto the cells
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Answer: D · Nonimmunologic protein adsorption onto the cells
Some drugs, including the beta-lactamase inhibitors clavulanate, sulbactam and tazobactam, alter the red cell membrane so that plasma proteins, including IgG and complement, stick to it without any antibody. This nonimmunologic protein adsorption gives a positive DAT, usually without hemolysis. The clue is that drug-treated cells react with normal plasma as well as the patient's, because no specific antibody is involved. A true drug antibody reacts with the patient's plasma but not with plasma from healthy people.
- A: A warm autoantibody would give a reactive eluate without any drug.
- B: Drug-in-solution antibodies are specific to the patient and usually cause brisk hemolysis.
- C: A hapten-type antibody is the patient's own, so healthy donors' plasma would not react.
Question 4 · Easy
The autoantibody in warm autoimmune hemolytic anemia is usually:
1. AIgM, reacting best at 4 °C
2. BIgG, reacting best at 4 °C
3. CIgM, reacting best at 37 °C
4. DIgG, reacting best at 37 °C
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Answer: D · IgG, reacting best at 37 °C
Warm AIHA, the most common form of autoimmune hemolytic anemia, is caused by an IgG autoantibody that binds best at body temperature. Coated red cells are removed by macrophages in the spleen, which leaves spherocytes in the blood. The DAT is positive with anti-IgG, sometimes with C3 as well, and the eluate usually reacts with all cells tested. About half of cases are secondary, for example to lymphoproliferative disorders or systemic lupus erythematosus.
- A: An IgM antibody reacting best at 4 °C is the cold agglutinin of cold agglutinin disease.
- B: An IgG antibody that binds in the cold is the biphasic Donath-Landsteiner antibody of paroxysmal cold hemoglobinuria.
- C: Warm-reacting IgM autoantibodies exist but are rare.
Question 5 · Hard
Two patients have anti-I. Patient 1: titer 2,048 at 4 °C, no reactivity above 20 °C. Patient 2: titer 128 at 4 °C, reacting at 30 °C in albumin. Which patient is more likely to have hemolysis, and why?
1. APatient 2, as the antibody reacts near body temperature
2. BNeither, as anti-I does not cause hemolysis
3. CBoth equally, as both antibodies are anti-I
4. DPatient 1, as the titer at 4 °C is much higher
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Answer: A · Patient 2, as the antibody reacts near body temperature
Whether a cold autoantibody causes hemolysis depends mainly on its thermal amplitude, the highest temperature at which it binds. An antibody that reacts at 30 °C or above can bind in the cooler skin and extremities, fix complement and destroy red cells. A high titer at 4 °C with no reactivity above 20 °C is typical of a harmless cold agglutinin. Thermal amplitude is tested with prewarmed samples and reagents at 30 °C and 37 °C, often in albumin to enhance the reactions.
- B: Pathologic anti-I is the usual cause of cold agglutinin disease.
- C: The temperature range matters more than the specificity of the antibody.
- D: A high titer at 4 °C alone does not predict hemolysis.
Question 6 · Medium
In cold agglutinin disease, the DAT is positive with anti-C3 only. An eluate made from the patient's red cells is usually:
1. ANonreactive, because the IgM leaves the cells
2. BReactive only with I-negative cord cells
3. CPanreactive at the antiglobulin phase
4. DReactive mainly with e-positive cells
Answer and explanation in LearnFree account
Question 7 · Medium
A patient with hemolysis has these results: DAT positive with anti-IgG and anti-C3; eluate reactive with all panel cells at the antiglobulin phase; a cold autoantibody with a titer of 32 at 4 °C that still reacts at 30 °C. Which diagnosis fits best?
1. AMixed-type autoimmune hemolytic anemia
2. BDelayed hemolytic transfusion reaction
3. CParoxysmal cold hemoglobinuria
4. DCold agglutinin disease
Answer and explanation in LearnFree account
Question 8 · Hard
A 19-year-old university student has had fever, sore throat and enlarged neck nodes for 10 days. Hemoglobin 98 g/L (9.8 g/dL), reticulocytes 7%, total bilirubin 46 µmol/L (2.7 mg/dL), LD raised; the film shows many reactive lymphocytes and red cell agglutinates. EBV VCA IgM is positive. DAT: anti-IgG negative, anti-C3d 2+. Cold agglutinin titers at 4 °C with group O cells: adult cells 16; cord blood cells 1,024; rare adult i cells 1,024. The autoantibody specificity and its cause are:
1. AAnti-I; Epstein-Barr virus infection
2. BAnti-i; Epstein-Barr virus infection
3. CAnti-I; Mycoplasma pneumoniae infection
4. DAnti-P; Donath-Landsteiner antibody
Answer and explanation in LearnFree account
Question 9 · Medium
An antibody reacts with all panel cells and the autocontrol at room temperature, but not at 37 °C or the antiglobulin phase. What is the most likely specificity?
1. AAn alloantibody such as anti-D
2. BAn alloantibody such as anti-Fya
3. CA cold autoantibody such as anti-I
4. DAn alloantibody such as anti-K
Answer and explanation in LearnFree account

Immune hemolytic anemias in the blood bank

A 40-year-old woman with warm AIHA has a hemoglobin of 62 g/L (6.2 g/dL), is stable, and needs transfusion. Every crossmatched unit reacts 2+ at the antiglobulin phase, and the resident asks for the least incompatible unit. What is the best response?

A blood sample is sent for a cold agglutinin titer. How should it be handled before the serum is separated?

A patient on piperacillin-tazobactam has a positive DAT with anti-IgG and anti-C3 but no hemolysis, and the eluate is nonreactive. Red cells treated with tazobactam alone react with the patient's plasma and also with plasma from several healthy donors. These findings point to:

The autoantibody in warm autoimmune hemolytic anemia is usually:

Two patients have anti-I. Patient 1: titer 2,048 at 4 °C, no reactivity above 20 °C. Patient 2: titer 128 at 4 °C, reacting at 30 °C in albumin. Which patient is more likely to have hemolysis, and why?

In cold agglutinin disease, the DAT is positive with anti-C3 only. An eluate made from the patient's red cells is usually:

A patient with hemolysis has these results: DAT positive with anti-IgG and anti-C3; eluate reactive with all panel cells at the antiglobulin phase; a cold autoantibody with a titer of 32 at 4 °C that still reacts at 30 °C. Which diagnosis fits best?

An antibody reacts with all panel cells and the autocontrol at room temperature, but not at 37 °C or the antiglobulin phase. What is the most likely specificity?