Many laboratories leave out the immediate-spin reading in the antibody screen. Why?

It mostly detects insignificant cold antibodies

It causes false negatives with anti-Jka

AABB Standards forbid immediate-spin reading

It is the only phase that detects anti-D

Antiglobulin-phase screen: cell I (D+C+E-c-e+, K-, Fy(a+b-), Jk(a+b-)) 2+; cell II (D+C-E+c+e-, K+, Fy(a-b+), Jk(a-b+)) 0; cell III (D-C-E-c+e+, K-, Fy(a+b+), Jk(a+b+)) 2+. Autocontrol 0. What can be concluded?

Anti-e, anti-Fya or anti-Jka; a panel is needed

Anti-D, because cells I and II are both D-positive

Anti-C, because cell I is C-positive

Anti-e alone, confirmed by this pattern

A patient's antibody screen is negative today, but records from another hospital show anti-Jka found 2 years ago. Which red cells should be given?

Jk(a-) units, crossmatched to the AHG phase

Units selected by electronic crossmatch

Jk(a-) units with an immediate-spin crossmatch

Any units, because today's screen is negative

A patient was transfused 4 weeks ago and needs blood again. How recent must the pretransfusion sample be?

Collected within 3 days of the transfusion

Collected within 7 days of the transfusion

Collected within 30 days of the transfusion

Collected within 24 hours of the transfusion

Reagent red cells for the patient antibody screen are:

Group O cells of known antigen types

Pooled cells from several group O donors

Routine tests: antibody detection (screen)

7 ASCP MLS practice questions on Routine tests: antibody detection (screen), part of Blood Banking. The first 7 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
Many laboratories leave out the immediate-spin reading in the antibody screen. Why?
1. AIt causes false negatives with anti-Jka
2. BAABB Standards forbid immediate-spin reading
3. CIt is the only phase that detects anti-D
4. DIt mostly detects insignificant cold antibodies
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Answer: D · It mostly detects insignificant cold antibodies
Antibodies that react only at immediate spin are usually IgM cold antibodies such as anti-M, anti-P1, anti-Lea or anti-I, which rarely cause hemolysis. Skipping this reading avoids time-consuming workups of antibodies that do not matter. Clinically significant antibodies react at 37 °C and the antiglobulin phase. ABO incompatibility is checked separately, by the crossmatch or an electronic system.
- A: Anti-Jka is detected at the antiglobulin phase, so skipping immediate spin does not miss it.
- B: AABB requires detection of clinically significant antibodies, not an immediate-spin reading.
- C: Anti-D is IgG and is detected at the antiglobulin phase.
Question 2 · Hard
Antiglobulin-phase screen: cell I (D+C+E-c-e+, K-, Fy(a+b-), Jk(a+b-)) 2+; cell II (D+C-E+c+e-, K+, Fy(a-b+), Jk(a-b+)) 0; cell III (D-C-E-c+e+, K-, Fy(a+b+), Jk(a+b+)) 2+. Autocontrol 0. What can be concluded?
1. AAnti-e, anti-Fya or anti-Jka; a panel is needed
2. BAnti-D, because cells I and II are both D-positive
3. CAnti-C, because cell I is C-positive
4. DAnti-e alone, confirmed by this pattern
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Answer: A · Anti-e, anti-Fya or anti-Jka; a panel is needed
Cells I and III react, and both carry e, Fya and Jka, which cell II lacks. The negative reaction with cell II argues against D, E, c, K, Fyb and Jkb. Three specificities, alone or together, still fit, so a full panel with selected cells is needed to separate them. A screen detects antibodies; it rarely identifies them.
- B: Cell II is D-positive and does not react, which argues against anti-D.
- C: Cell III lacks C but still reacts, so anti-C alone does not fit.
- D: The same pattern fits anti-Fya or anti-Jka, so anti-e is not confirmed.
Question 3 · Hard
A patient's antibody screen is negative today, but records from another hospital show anti-Jka found 2 years ago. Which red cells should be given?
1. AJk(a-) units, crossmatched to the AHG phase
2. BUnits selected by electronic crossmatch
3. CJk(a-) units with an immediate-spin crossmatch
4. DAny units, because today's screen is negative
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Answer: A · Jk(a-) units, crossmatched to the AHG phase
Kidd antibodies often fall below detectable levels but return quickly after re-exposure, causing delayed hemolysis. A clinically significant antibody found in the past is honored for life, with antigen-negative units. An antiglobulin crossmatch is also required because of the antibody history. Sharing antibody records between hospitals prevents these reactions.
- B: Electronic crossmatch is not allowed with a history of a clinically significant antibody.
- C: An immediate-spin crossmatch does not detect IgG incompatibility.
- D: A negative screen does not rule out an evanescent anti-Jka.
Question 4 · Medium
A patient was transfused 4 weeks ago and needs blood again. How recent must the pretransfusion sample be?
1. ACollected within 7 days of the transfusion
2. BCollected within 30 days of the transfusion
3. CCollected within 3 days of the transfusion
4. DCollected within 24 hours of the transfusion
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Answer: C · Collected within 3 days of the transfusion
If a patient has been transfused or pregnant in the past 3 months, or the history is unknown, a new antibody can appear quickly. AABB therefore requires the sample to be collected within 3 days of the planned transfusion. Many laboratories count the day of collection as day 0. Patients with no recent exposure may follow a longer window set by local policy.
- A: 7 days is too long after a recent transfusion.
- B: 30 days is far too long for a recently transfused patient.
- D: 24 hours is stricter than the standard requires.
Question 5 · Easy
Reagent red cells for the patient antibody screen are:
1. AThe patient's own red cells
2. BGroup A and group B cells
3. CGroup O cells of known antigen types
4. DPooled cells from several group O donors
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Answer: C · Group O cells of known antigen types
Screening cells are group O so that the patient's anti-A and anti-B do not react. Two or three cells are used, chosen so that the set carries the antigens of common clinically significant antibodies. Cells homozygous for antigens such as Jka or Fya help detect weak antibodies. Each lot comes with a sheet listing every cell's antigens.
- A: Testing the patient's own cells is the autocontrol.
- B: Group A and B cells are used for reverse ABO grouping.
- D: Pooled cells are allowed only for donor testing.
Question 6 · Medium
Why are pooled screening cells not used for patient antibody screens?
1. APooled cells lack the Rh antigens
2. BPooled cells are hemolyzed by storage
3. CPooled cells always include some group A cells
4. DWeak antibodies can be missed through dilution
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Question 7 · Hard
A 45-year-old woman with two children has a type and screen before a hysterectomy; she has never been transfused. In the PEG antiglobulin test, screening cells I, II and III each react 1+, and the autocontrol is negative. Her DAT is negative. An 11-cell panel from the same manufacturer reacts 1+ with every cell. Antiglobulin crossmatches in PEG with segments from two ABO-compatible donor units are compatible. When the same screening cells are washed three times in saline before testing, all three are nonreactive. The most likely explanation is:
1. AAntibody to a reagent-cell preservative
2. BAntibody to a high-prevalence antigen
3. CCold autoantibody with anti-I specificity
4. DWarm autoantibody with a negative DAT
Answer and explanation in LearnFree account