Panel cells react at the antiglobulin phase with strengths from 1+ to 3+, several cells are nonreactive, and the autocontrol is negative. This pattern most likely means:

More than one alloantibody is present

A warm autoantibody coats the cells

A cold autoantibody such as anti-I

An antibody to a high-prevalence antigen

To confirm an antibody's specificity by the 'rule of three', the plasma should:

React with 3 antigen-positive cells but not 3 negative cells

React with every cell of a panel at the same strength

React with just 1 antigen-positive cell but not 1 negative cell

React with any 3 cells at the antiglobulin phase

During antibody identification, an antigen is usually 'ruled out' when:

A cell carrying it, ideally homozygous, is nonreactive

A cell carrying it reacts at the antiglobulin phase

A cell lacking it reacts at the antiglobulin phase

It is present on at least one screening cell

Routine tests: antibody identification and clinical significance

22 ASCP MLS practice questions on Routine tests: antibody identification and clinical significance, part of Blood Banking. The first 22 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 · Medium
Panel cells react at the antiglobulin phase with strengths from 1+ to 3+, several cells are nonreactive, and the autocontrol is negative. This pattern most likely means:
1. AA warm autoantibody coats the cells
2. BMore than one alloantibody is present
3. CA cold autoantibody such as anti-I
4. DAn antibody to a high-prevalence antigen
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Answer: B · More than one alloantibody is present
Reactions of different strength, with some negative cells, are typical of a mixture of alloantibodies, each reacting with its own antigen-positive cells. Dosage can also cause some variation. A negative autocontrol makes an autoantibody unlikely. Selected cells, enzyme-treated or DTT-treated cells, and adsorption help separate the antibodies.
- A: A warm autoantibody would usually react with all cells and make the autocontrol positive.
- C: A cold autoantibody would react at room temperature and with the autocontrol.
- D: An antibody to a high-prevalence antigen would react with nearly every cell, usually evenly.
Question 2 · Medium
A patient with no transfusion in the past 3 months has anti-K identified on a panel. Which result on the patient's own red cells supports the identification?
1. AThe autocontrol is positive
2. BThe DAT is positive
3. CK typing is positive
4. DK typing is negative
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Answer: D · K typing is negative
People normally make alloantibodies only to antigens they lack, so a K-negative typing supports anti-K. If the patient typed K-positive, an autoantibody, a variant antigen or a typing problem would need to be considered. The typing must be done on a sample free of recently transfused cells. About 91% of donors are K-negative, so compatible units are easy to find.
- A: A positive autocontrol suggests an autoantibody or coated cells, not alloanti-K.
- B: A positive DAT points to antibody on the patient's own cells, not to alloanti-K.
- C: A K-positive patient would not usually make alloanti-K, so this would cast doubt on the result.
Question 3 · Easy
To confirm an antibody's specificity by the 'rule of three', the plasma should:
1. AReact with every cell of a panel at the same strength
2. BReact with 3 antigen-positive cells but not 3 negative cells
3. CReact with just 1 antigen-positive cell but not 1 negative cell
4. DReact with any 3 cells at the antiglobulin phase
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Answer: B · React with 3 antigen-positive cells but not 3 negative cells
Three reactive antigen-positive cells and three nonreactive antigen-negative cells give a probability of about 1 in 20 or less that the pattern arose by chance. This is the usual standard for confirming a single specificity. Extra selected cells are tested when the panel does not meet it. The patient's red cells should also type negative for the antigen.
- A: Uniform reactions with every cell suggest a high-prevalence or autoantibody, not a confirmed specificity.
- C: One positive and one negative cell could match by chance far too often.
- D: Three reactive cells without matching negative cells prove nothing about specificity.
Question 4 · Hard
Antiglobulin-phase panel (assume nonreactive cells are homozygous). Cell 1: E+ K- Fya+ Jkb+ 2+. Cell 2: E- K+ Fya- Jkb+ 2+. Cell 3: E- K- Fya+ Jkb+ 0. Cell 4: E+ K+ Fya- Jkb- 3+. Cell 5: E- K- Fya- Jkb+ 0. Cell 6: E- K- Fya+ Jkb- 0. The autocontrol is negative. The most likely antibodies are:
1. AAnti-Fya and anti-Jkb
2. BAnti-K alone
3. CAnti-E and anti-K
4. DAnti-E alone
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Answer: C · Anti-E and anti-K
Fya is ruled out by cells 3 and 6, and Jkb by cells 3 and 5. Anti-E alone cannot explain cell 2, which is E- but reacts, and anti-K alone cannot explain cell 1, which is K- but reacts. Both antibodies together explain every result, and cell 4, which carries both antigens, reacts most strongly. More E+K- and K+E- cells are needed to meet the rule of three for each, and the patient should type E- and K-.
- A: Fya and Jkb are carried by nonreactive cells, so both are ruled out.
- B: Anti-K alone does not explain the reaction of K- cell 1.
- D: Anti-E alone does not explain the reaction of E- cell 2.
Question 5 · Easy
During antibody identification, an antigen is usually 'ruled out' when:
1. AA cell carrying it reacts at the antiglobulin phase
2. BA cell lacking it reacts at the antiglobulin phase
3. CA cell carrying it, ideally homozygous, is nonreactive
4. DIt is present on at least one screening cell
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Answer: C · A cell carrying it, ideally homozygous, is nonreactive
If the plasma does not react with a cell that carries an antigen, an antibody to that antigen is unlikely. Cells homozygous for the antigen are preferred for antigens that show dosage, so a weak antibody is not wrongly excluded. Antigens that are not ruled out remain candidates. The specificity is then confirmed with the rule of three and by typing the patient.
- A: A reacting antigen-positive cell keeps the antigen as a candidate; it does not exclude it.
- B: A reacting antigen-negative cell points to another antibody; it does not exclude this one.
- D: Presence on a screening cell means nothing until that cell's reaction is known.
Question 6 · Hard
A patient transfused 3 weeks ago now has anti-Fya. Today the patient's red cells type Fy(a+), with weak, mixed-field reactions. The best explanation and next step is:
1. AThe patient made an autoantibody; give Fy(a+) units
2. BDonor cells are being typed; genotype the patient
3. CThe typing is reliable, so anti-Fya is a false positive
4. DFya antigen weakens with age; no action is needed
Answer and explanation in LearnFree account
Question 7 · Hard
Before elective surgery, a patient's anti-P1 reacts only at immediate spin; tests at 37 °C and the antiglobulin phase are negative. Which red cells are suitable?
1. AUnits compatible at 37 °C and the AHG phase
2. BOnly P1-negative units, confirmed by typing
3. CWashed units, to avoid any P1 reaction
4. DGroup O units, which lack the P1 antigen
Answer and explanation in LearnFree account
Question 8 · Medium
A patient transfused 10 days ago has a positive autocontrol at the antiglobulin phase and a new antibody in the plasma. What should be considered first?
1. AAlloantibody coating the transfused donor cells
2. BA technical error in the antiglobulin test
3. CA warm autoantibody unrelated to transfusion
4. DRouleaux caused by the patient's plasma proteins
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Question 9 · Hard
Panel results suggest anti-S: S+s- cells react 1+, while one S+s+ cell is nonreactive. Other antibodies are excluded. The best interpretation is:
1. AA weak anti-S showing dosage; test more S+s- cells
2. BThe antigram for the S+s+ cell must be wrong
3. CAnti-S is excluded by the nonreactive S+s+ cell
4. DAnti-s is present instead of anti-S
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Question 10 · Medium
Why should anti-Jka, anti-Fya and anti-E be ruled out with cells homozygous for the antigen whenever possible?
1. AHeterozygous cells lack the antigen entirely
2. BHomozygous cells react at room temperature
3. COnly homozygous cells bind complement
4. DWeak antibodies may miss heterozygous cells
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Question 11 · Medium
Which antibody is usually clinically significant, so that antigen-negative red cells are given?
1. AAnti-Fya
2. BAnti-P1
3. CAnti-N
4. DAnti-Lea
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Question 12 · Hard
Antiglobulin-phase panel (assume nonreactive cells are homozygous for their antigens). Cell 1: K+ Fya+ Jka+ E- 2+. Cell 2: K- Fya+ Jka+ E+ 0. Cell 3: K+ Fya- Jka- E- 2+. Cell 4: K- Fya- Jka+ E+ 0. Cell 5: K+ Fya+ Jka- E+ 2+. Cell 6: K- Fya+ Jka- E- 0. The autocontrol is negative. Which antibody is present?
1. AAnti-Fya
2. BAnti-E
3. CAnti-Jka
4. DAnti-K
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Question 13 · Hard
A patient types R1R1 (DCe/DCe). The panel shows anti-c, and c+E+ cells react slightly more strongly than c+E- cells. Which red cells should be given?
1. Ac-negative, E-negative (R1R1) units
2. Bc-negative units, whatever their E type
3. CD-negative units, whatever their c type
4. DE-negative units, whatever their c type
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Question 14 · Hard
In a tube panel using fresh serum, several Jk(a+) cells show partial hemolysis with few agglutinates, while Jk(a-) cells are clear. How should the hemolyzed tubes be read?
1. AAs caused by sample contamination
2. BAs invalid tests to discard
3. CAs positive reactions
4. DAs negative reactions
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Question 15 · Hard
A 34-year-old man whose red cells type rr (dce/dce) received D-positive red cells in an emergency 4 months ago and now has a positive antibody screen. On an 11-cell antiglobulin panel, all seven D-positive cells react 2+ to 3+; these include every C-positive and every E-positive cell on the panel. The four D-negative cells, all rr, are nonreactive; among them are a K+ cell and cells homozygous for Fya, Fyb, Jka, Jkb, S and s. The autocontrol is negative. Before the identification is complete, which testing is needed?
1. ATesting r'r and r''r selected cells
2. BTesting ficin-treated panel cells
3. CPhenotyping his cells for C and E
4. DTesting DTT-treated panel cells
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Question 16 · Hard
A 59-year-old man transfused a year ago has a positive antibody screen. Antiglobulin panel, untreated / ficin-treated cells (assume nonreactive cells are homozygous for their antigens). Cell 1: E+ K- Fya+ Jka- S-, 2+ / 3+. Cell 2: E- K- Fya+ Jka- S+, 2+ / 0. Cell 3: E+ K- Fya- Jka+ S-, 2+ / 3+. Cell 4: E- K+ Fya- Jka+ S+, 0 / 0. Cell 5: E- K- Fya- Jka- S-, 0 / 0. Cell 6: E+ K- Fya- Jka- S+, 2+ / 3+. Cell 7: E- K- Fya+ Jka+ S-, 2+ / 0. Autocontrol 0 / 0. Which antibodies are present?
1. AAnti-E alone
2. BAnti-Fya and anti-Jka
3. CAnti-E and anti-S
4. DAnti-E and anti-Fya
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Question 17 · Medium
A patient's plasma was tested against the panel shown by a LISS tube method. Which antibody explains every reaction?
Figure: MedExams
1. AAnti-Fya
2. BAnti-c
3. CAnti-K
4. DAnti-E
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Question 18 · Medium
A 52-year-old woman with anemia has never been transfused. Her antibody screen is positive, and the panel shown is tested. The most likely cause of these reactions is:
Figure: MedExams
1. ASeveral alloantibodies
2. BAn antibody to a high-prevalence antigen
3. CA warm autoantibody
4. DA cold autoantibody
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Question 19 · Medium
A 40-year-old man has a positive antibody screen before knee surgery. Based on the panel shown, the antibody and its transfusion requirement are:
Figure: MedExams
1. AAnti-N; antigen-negative units are not required
2. BAnti-M; M-negative units must be given
3. CAnti-M; antigen-negative units are not required
4. DAnti-P1; P1-negative units must be given
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Question 20 · Hard
A 58-year-old woman transfused 6 weeks ago has a positive antibody screen and a negative DAT. Refer to the panel shown. The reactions are best explained by:
Figure: MedExams
1. AAnti-S, showing dosage
2. BAn antibody to a low-prevalence antigen
3. CAnti-Jka, showing dosage
4. DAnti-Fya, showing dosage
Answer and explanation in LearnFree account
Question 21 · Hard
Refer to the panel shown. The patient's own red cells type E-negative and K-negative. Which antibodies are present?
Figure: MedExams
1. AAnti-K alone
2. BAnti-E and anti-Fya
3. CAnti-E and anti-K
4. DAnti-c and anti-K
Answer and explanation in LearnFree account
Question 22 · Medium
An antibody reacts more strongly with Jk(a+b-) red cells than with Jk(a+b+) red cells. What is this effect called?
1. AProzone
2. BNeutralization
3. CDosage
4. DEnhancement
Answer and explanation in LearnFree account

Routine tests: antibody identification and clinical significance

Panel cells react at the antiglobulin phase with strengths from 1+ to 3+, several cells are nonreactive, and the autocontrol is negative. This pattern most likely means:

A patient with no transfusion in the past 3 months has anti-K identified on a panel. Which result on the patient's own red cells supports the identification?

To confirm an antibody's specificity by the 'rule of three', the plasma should:

Antiglobulin-phase panel (assume nonreactive cells are homozygous). Cell 1: E+ K- Fya+ Jkb+ 2+. Cell 2: E- K+ Fya- Jkb+ 2+. Cell 3: E- K- Fya+ Jkb+ 0. Cell 4: E+ K+ Fya- Jkb- 3+. Cell 5: E- K- Fya- Jkb+ 0. Cell 6: E- K- Fya+ Jkb- 0. The autocontrol is negative. The most likely antibodies are:

During antibody identification, an antigen is usually 'ruled out' when:

A patient transfused 3 weeks ago now has anti-Fya. Today the patient's red cells type Fy(a+), with weak, mixed-field reactions. The best explanation and next step is:

Before elective surgery, a patient's anti-P1 reacts only at immediate spin; tests at 37 °C and the antiglobulin phase are negative. Which red cells are suitable?

A patient transfused 10 days ago has a positive autocontrol at the antiglobulin phase and a new antibody in the plasma. What should be considered first?

Panel results suggest anti-S: S+s- cells react 1+, while one S+s+ cell is nonreactive. Other antibodies are excluded. The best interpretation is:

Why should anti-Jka, anti-Fya and anti-E be ruled out with cells homozygous for the antigen whenever possible?

Which antibody is usually clinically significant, so that antigen-negative red cells are given?

A patient types R1R1 (DCe/DCe). The panel shows anti-c, and c+E+ cells react slightly more strongly than c+E- cells. Which red cells should be given?

In a tube panel using fresh serum, several Jk(a+) cells show partial hemolysis with few agglutinates, while Jk(a-) cells are clear. How should the hemolyzed tubes be read?

A patient's plasma was tested against the panel shown by a LISS tube method. Which antibody explains every reaction?

A 52-year-old woman with anemia has never been transfused. Her antibody screen is positive, and the panel shown is tested. The most likely cause of these reactions is:

A 40-year-old man has a positive antibody screen before knee surgery. Based on the panel shown, the antibody and its transfusion requirement are:

A 58-year-old woman transfused 6 weeks ago has a positive antibody screen and a negative DAT. Refer to the panel shown. The reactions are best explained by:

Refer to the panel shown. The patient's own red cells type E-negative and K-negative. Which antibodies are present?

An antibody reacts more strongly with Jk(a+b-) red cells than with Jk(a+b+) red cells. What is this effect called?