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ASCP SBB practice questions

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Question 1Blood Banking / Immunohematology Theory and Serology

A person with blood group B is expected to have which antibody in serum?

  1. Anti-D
  2. Anti-A Correct answer.
  3. Anti-A and anti-B
  4. Anti-B

Explanation

Landsteiner's rule states that individuals form IgM antibodies against ABH antigens absent from their red cells. Group B red cells carry B antigen, so the serum contains anti-A. Anti-B would be an autoantibody and is not expected.

Question 2Blood Banking / Immunohematology Theory and Serology

Which red cell antigen is considered the most immunogenic after the ABO system?

  1. K (Kell)
  2. Jka (Kidd)
  3. Fya (Duffy)
  4. D (Rh) Correct answer.

Explanation

RhD is highly immunogenic; a large proportion of D-negative people exposed to D-positive red cells form anti-D. Kell, Duffy, and Kidd antigens are immunogenic but considerably less so than D.

Question 3Blood Banking / Immunohematology Theory and Serology

Which immunoglobulin class is transported across the placenta and can cause hemolytic disease of the fetus and newborn?

  1. IgM
  2. IgG Correct answer.
  3. IgA
  4. IgE

Explanation

IgG is actively transported across the placenta by the neonatal Fc receptor, so IgG red cell antibodies can reach the fetal circulation and cause hemolysis. IgM and IgA do not cross the placenta in significant amounts.

Question 4Blood Banking / Immunohematology Theory and Serology

The direct antiglobulin test is used to detect which of the following?

  1. Unexpected antibodies circulating in patient serum
  2. RBC-bound IgG and/or complement in vivo Correct answer.
  3. Complement only
  4. Antibody titer

Explanation

The direct antiglobulin test uses antihuman globulin to cross-link IgG or complement already bound to red cells in the patient's circulation. It demonstrates in vivo sensitization, as seen in autoimmune hemolysis or hemolytic transfusion reactions.

Question 5Blood Banking / Immunohematology Theory and Serology

Bombay (Oh) phenotype red cells lack which antigen?

  1. A antigen
  2. D antigen
  3. H antigen Correct answer.
  4. B antigen

Explanation

Bombay individuals lack H antigen because of inactivating mutations in FUT1, so they cannot express A or B antigens and form potent anti-H. The defining absence is H, the precursor for A and B.

Question 6Blood Banking / Immunohematology Theory and Serology

Lewis antigens on red cells are primarily which of the following?

  1. Adsorbed from plasma lipoproteins Correct answer.
  2. Encoded by RH genes
  3. Glycolipids intrinsic to the red cell membrane
  4. Synthesized by red cell precursors

Explanation

Lewis antigens are synthesized by exocrine epithelial cells and circulate in plasma, then adsorb onto red cells. They are not intrinsic to the red cell membrane, which explains why Lewis phenotype can change and why Lewis antibodies are often neutralized by plasma or saliva.

Question 7Blood Banking / Immunohematology Theory and Serology

The antibody screening test is performed to detect which of the following?

  1. Unexpected antibodies in patient serum or plasma Correct answer.
  2. ABO incompatibility detected by forward and reverse typing
  3. Antigen frequency in the donor population
  4. Red cell-bound complement

Explanation

The antibody screen incubates patient serum or plasma with reagent red cells of known phenotype to detect clinically significant unexpected antibodies. ABO typing and the direct antiglobulin test are separate procedures.

Question 8Blood Banking / Immunohematology Theory and Serology

Anti-I cold agglutinins react optimally at which temperature?

  1. 56°C
  2. 37°C
  3. 22°C
  4. 4°C Correct answer.

Explanation

Cold agglutinins such as anti-I are IgM antibodies that bind best near 4°C and usually dissociate at 37°C. They are generally not clinically significant unless present in high titer with a wide thermal amplitude.

Question 9Blood Banking / Immunohematology Theory and Serology

Proteolytic enzymes such as ficin and papain typically destroy which red cell antigens?

  1. Fya and Fyb Correct answer.
  2. K and k
  3. D and Jka
  4. Lea and Leb

Explanation

Proteases cleave sialic acid-rich glycoproteins, destroying Duffy antigens Fya and Fyb as well as MNS antigens. They enhance many Rh, Kidd, and Lewis antigens, which helps in antibody identification.

Question 10Blood Banking / Immunohematology Theory and Serology

Anti-Jka typically shows dosage, meaning that it reacts how?

  1. Only at 4°C
  2. Only with enzyme-treated cells
  3. Equally with Jk(a+) and Jk(a-) cells regardless of zygosity
  4. More strongly with homozygous Jk(a+b-) cells Correct answer.

Explanation

Kidd antibodies characteristically show dosage, reacting more strongly with red cells homozygous for the antigen than with heterozygous cells. This can cause weak or missed reactions if only heterozygous cells are used.

Question 11Blood Banking / Immunohematology Theory and Serology

LISS is used in the indirect antiglobulin test primarily to do which of the following?

  1. Increase the rate of antibody uptake onto red cells Correct answer.
  2. Destroy IgM antibodies by reducing disulfide bonds
  3. Stabilize red cells at 56°C
  4. Prevent complement activation

Explanation

Low-ionic-strength solution reduces the zeta potential around red cells, allowing antibodies to bind faster and shortening incubation time. It does not destroy antibodies or prevent complement activation.

Question 12Blood Banking / Immunohematology Theory and Serology

In an anti-human globulin gel card, what is detected as red cells pass through the gel?

  1. Free hemoglobin released from red cells that have been lysed
  2. ABO antigens directly by the gel matrix
  3. IgG bound to red cells as they pass through the gel Correct answer.
  4. Only IgM antibodies

Explanation

In the AHG gel card, anti-human globulin is incorporated into the gel. Red cells coated with IgG are cross-linked and trapped in the gel, while uncoated cells pass through.

Question 13Blood Banking / Immunohematology Theory and Serology

Which elution method uses an acidic glycine-HCl buffer to dissociate IgG from red cells?

  1. Chloroquine diphosphate treatment
  2. Freeze-thaw lysis
  3. Heat elution at 56°C
  4. Acid elution (glycine-HCl) Correct answer.

Explanation

Acid elution uses low pH to dissociate red cell-bound IgG, and the eluate is then neutralized before testing. Heat elution relies on temperature rather than acid and is often used for IgM antibodies.

Question 14Blood Banking / Immunohematology Theory and Serology

In a patient with a warm autoantibody, differential allogeneic adsorption is performed to do which of the following?

  1. Increase the titer of the autoantibody in the patient's serum
  2. Detect complement bound to red cells
  3. Determine the patient's Rh phenotype
  4. Remove autoantibody and reveal underlying alloantibody Correct answer.

Explanation

Differential adsorption uses allogeneic red cells of known phenotype to adsorb the warm autoantibody while leaving any underlying alloantibody in the adsorbed serum. The adsorbed serum is then tested against a panel to detect the alloantibody.

Question 15Blood Banking / Immunohematology Theory and Serology

Detection of red cell-bound complement in the direct antiglobulin test is best accomplished with which reagent?

  1. Anti-IgG only
  2. Anti-albumin reagent used for a different purpose
  3. Monospecific anti-C3d (or anti-C3b/C3d) Correct answer.
  4. Anti-IgM

Explanation

Complement activation on red cells leaves C3d covalently bound to the membrane, and monospecific anti-C3d detects it. Polyspecific antihuman globulin contains both anti-IgG and anti-C3d.

Question 16Blood Banking / Immunohematology Theory and Serology

Weak D testing is performed by incubating red cells with anti-D followed by which procedure?

  1. Enzyme treatment only
  2. Immediate spin only
  3. Indirect antiglobulin test Correct answer.
  4. 4°C overnight incubation followed by no AHG

Explanation

Weak D testing requires an IgG anti-D reagent and the indirect antiglobulin test because weak D red cells express reduced D antigen and are not agglutinated at immediate spin. This method detects weak expression of the D antigen.

Question 17Blood Banking / Immunohematology Theory and Serology

Anti-K (Kell) is clinically significant primarily because it does which of the following?

  1. Can cause severe HDFN and hemolytic transfusion reactions Correct answer.
  2. Reacts only with enzyme-treated red cells and not untreated cells
  3. Is naturally occurring
  4. Is an IgM antibody that reacts at room temperature

Explanation

Anti-K is an IgG antibody that persists and can cause severe hemolytic disease of the fetus and newborn, sometimes even at low titer, as well as delayed hemolytic transfusion reactions. K antigen is highly immunogenic.

Question 18Blood Banking / Immunohematology Theory and Serology

The Fy(a-b-) phenotype is common in people of West African descent and confers resistance to which organism?

  1. Parvovirus B19
  2. Babesia microti
  3. Epstein-Barr virus
  4. Plasmodium falciparum Correct answer.

Explanation

Duffy-negative red cells lack the Fy6 receptor used by Plasmodium falciparum merozoites, so the phenotype is protective against malaria. This explains the high frequency of Fy(a-b-) in malaria-endemic regions.

Question 19Blood Banking / Immunohematology Theory and Serology

When ruling out an antibody specificity on a red cell panel, which cells should be used for antigens showing dosage?

  1. Any cell available on the panel
  2. Cells heterozygous for the antigen
  3. Cells homozygous for the antigen (for dosage systems) Correct answer.
  4. Cells lacking the antigen, which are used to confirm a specificity

Explanation

Many antibodies show dosage and may react weakly or not at all with heterozygous cells. A negative reaction with a homozygous antigen-positive cell is required to validly rule out the antibody.

Question 20Blood Banking / Immunohematology Theory and Serology

A prewarm technique is used in antibody testing to do which of the following?

  1. Detect complement
  2. Enhance IgG antibody binding
  3. Avoid detection of clinically insignificant cold autoantibodies Correct answer.
  4. Increase the incubation temperature to 56°C to mimic heat elution conditions

Explanation

In the prewarm technique, serum and red cells are warmed to 37°C before mixing and kept at 37°C throughout incubation. Cold-reactive IgM antibodies do not bind at this temperature, reducing interference from clinically insignificant cold autoantibodies.

Question 21Blood Banking / Immunohematology Theory and Serology

Dithiothreitol treatment of serum is used to do which of the following?

  1. Inactivate IgM and denature Kell antigens Correct answer.
  2. Destroy only IgG antibodies while preserving IgM activity
  3. Enhance complement binding to red cells
  4. Increase the titer of warm autoantibodies

Explanation

Dithiothreitol reduces disulfide bonds, denaturing pentameric IgM while IgG is relatively resistant. It also denatures Kell antigens, so DTT-treated cells cannot be used to rule out anti-K.

Question 22Blood Banking / Immunohematology Theory and Serology

The Vel antigen is a high-frequency antigen against which clinically significant anti-Vel can be formed. Which gene encodes the Vel antigen?

  1. SMIM1 Correct answer.
  2. ACKR1 (DARC)
  3. RHCE
  4. GYPA

Explanation

Vel is encoded by SMIM1, which produces a small integral membrane protein. Vel-negative individuals can form anti-Vel, an antibody that has caused severe hemolytic transfusion reactions.

Question 23Blood Banking / Immunohematology Theory and Serology

Paroxysmal nocturnal hemoglobinuria red cells are abnormally sensitive to complement because they lack which proteins?

  1. Factor H
  2. C4 binding protein, which regulates the classical pathway in plasma
  3. CR1
  4. CD55 and CD59 (GPI-anchored regulators) Correct answer.

Explanation

Paroxysmal nocturnal hemoglobinuria results from PIGA mutations that prevent GPI anchor synthesis, so red cells lack CD55 and CD59. Without these regulators, complement activation proceeds uncontrolled and causes intravascular hemolysis.

Question 24Blood Banking / Immunohematology Theory and Serology

Which IgG subclasses efficiently activate complement and bind Fc receptors on macrophages, making them most relevant to red cell hemolysis?

  1. IgG2 and IgG4
  2. IgG2 and IgG3
  3. IgG1 and IgG3 Correct answer.
  4. IgG1 and IgG4

Explanation

IgG1 and IgG3 fix complement and bind monocyte Fc gamma receptors well, so they mediate red cell destruction most effectively. Most clinically significant red cell alloantibodies belong to these subclasses.

Question 25Blood Banking / Immunohematology Theory and Serology

Dolichos biflorus lectin agglutinates which red cells?

  1. A1 cells but not A2 cells Correct answer.
  2. A2 cells but not A1 cells
  3. B cells
  4. O cells

Explanation

Dolichos biflorus contains anti-A1 lectin and agglutinates A1 cells but not A2 cells. It is used to distinguish A1 from A2 and to help identify anti-A1 in A2 individuals.

Question 26Blood Banking / Immunohematology Theory and Serology

Which immunoglobulin class is responsible for the naturally occurring anti-A and anti-B antibodies found in serum?

  1. IgE
  2. IgM Correct answer.
  3. IgA
  4. IgG

Explanation

ABO isoagglutinins are predominantly IgM antibodies. They are pentameric, react well in saline at room temperature, and efficiently activate complement.

Question 27Blood Banking / Immunohematology Theory and Serology

After the ABO system, which red cell antigen is generally considered the most immunogenic?

  1. Kell (K)
  2. Duffy (Fya)
  3. D (Rh) Correct answer.
  4. Kidd (Jka)

Explanation

D is highly immunogenic and is the most common cause of severe hemolytic disease of the fetus and newborn and hemolytic transfusion reactions outside ABO. Other red cell antigens can be immunogenic but are less so than D.

Question 28Blood Banking / Immunohematology Theory and Serology

Which immunoglobulin class is most commonly responsible for clinically significant hemolytic disease of the fetus and newborn?

  1. IgE
  2. IgG Correct answer.
  3. IgA
  4. IgM

Explanation

IgG antibodies cross the placenta by interacting with neonatal Fc receptors and can bind fetal red cells. IgM antibodies are too large to cross the placenta efficiently.

Question 29Blood Banking / Immunohematology Theory and Serology

Which anticoagulant is preferred for collecting a blood sample for the direct antiglobulin test when complement sensitization is suspected?

  1. Sodium citrate
  2. EDTA Correct answer.
  3. Acid-citrate-dextrose
  4. Heparin

Explanation

EDTA chelates calcium and prevents in vitro complement activation on red cells. This helps preserve the in vivo sensitization pattern for DAT interpretation.

Question 30Blood Banking / Immunohematology Theory and Serology

An antibody reacts with untreated panel cells at room temperature and 4°C, shows dosage, and does not react with ficin-treated cells. Which antibody is most likely?

  1. Anti-Jka
  2. Anti-M Correct answer.
  3. Anti-K
  4. Anti-D

Explanation

Anti-M is a cold-reactive antibody that often shows dosage and is destroyed by proteolytic enzymes such as ficin. Anti-D, anti-K, and anti-Jka are typically reactive at 37°C or AHG and are not enzyme-labile in this pattern.

Question 31Blood Banking / Immunohematology Theory and Serology

Why do IgM antibodies agglutinate red cells directly in saline, whereas IgG antibodies usually require antihuman globulin?

  1. IgM has a higher affinity for red cell antigens than IgG
  2. IgM is pentameric and can bridge antigen sites on adjacent red cells Correct answer.
  3. IgG is rapidly destroyed by complement in saline
  4. IgM antibodies are found only at 4°C

Explanation

IgM molecules are pentamers with multiple antigen-binding sites, allowing them to span the distance between red cells and cause direct agglutination. IgG monomers are smaller and generally cannot bridge red cells without antihuman globulin.

Question 32Blood Banking / Immunohematology Theory and Serology

Autologous adsorption for antibody identification is generally contraindicated in which situation?

  1. The patient has a negative direct antiglobulin test
  2. The patient was transfused within the previous 3 months Correct answer.
  3. The patient has a warm autoantibody
  4. The patient has a cold agglutinin

Explanation

Recent transfusion introduces donor red cells that can adsorb alloantibody, leading to a false-negative antibody identification. In that setting, allogeneic adsorption with selected donor cells is used instead.

Question 33Blood Banking / Immunohematology Theory and Serology

Chloroquine diphosphate is used in immunohematology to do which of the following?

  1. Precipitate fibrin from plasma samples
  2. Inactivate IgM antibodies in serum
  3. Remove IgG from sensitized red cells to allow phenotyping Correct answer.
  4. Enhance antigen expression on enzyme-treated red cells

Explanation

Chloroquine diphosphate dissociates IgG from red cell membranes without lysing the cells, allowing antigen phenotyping of DAT-positive red cells. It is not an antibody-enhancing or IgM-inactivating reagent.

Question 34Blood Banking / Immunohematology Theory and Serology

What is the purpose of adding IgG-sensitized red cells at the end of an indirect antiglobulin test?

  1. To confirm that antihuman globulin reagent was added and remains active Correct answer.
  2. To provide a positive control for the antibody screen itself
  3. To neutralize free complement in the patient serum
  4. To enhance weak IgG antibody binding to panel cells

Explanation

IgG-sensitized red cells, often called check cells, agglutinate if active antihuman globulin is present. If they fail to agglutinate, the AHG test is invalid and must be repeated.

Question 35Blood Banking / Immunohematology Theory and Serology

Antibodies to Kidd system antigens are clinically important because they characteristically do which of the following?

  1. Cause immediate intravascular hemolysis as IgM antibodies
  2. React only at 4°C and never at 37°C
  3. Disappear below detectable levels and cause delayed hemolytic transfusion reactions Correct answer.
  4. Fix complement but are not clinically significant

Explanation

Kidd antibodies often become undetectable over time but show an anamnestic response after transfusion, causing delayed hemolytic transfusion reactions. They can activate complement and are clinically significant.

Question 36Blood Banking / Immunohematology Theory and Serology

A group O mother delivers a group A infant with mild jaundice on day 2. The infant's DAT is weakly positive, and an eluate reacts with A1 cells. Which condition is most likely?

  1. Rh hemolytic disease of the fetus and newborn
  2. Glucose-6-phosphate dehydrogenase deficiency
  3. Hereditary spherocytosis
  4. ABO hemolytic disease of the fetus and newborn Correct answer.

Explanation

ABO HDFN typically occurs in group O mothers with group A or B infants and is often milder than Rh HDFN. The eluate reactivity with A1 cells supports maternal anti-A coating the infant's red cells.

Question 37Blood Banking / Immunohematology Theory and Serology

A patient with a partial D phenotype is transfused with D-positive red cells. What is the main concern?

  1. Hyperkalemia
  2. Febrile nonhemolytic transfusion reaction
  3. Iron overload
  4. Anti-D alloimmunization Correct answer.

Explanation

Partial D red cells lack some D epitopes, so exposure to a full D-positive red cell unit can stimulate anti-D. Patients with partial D are generally managed as D-negative for transfusion.

Question 38Blood Banking / Immunohematology Theory and Serology

A patient's serum agglutinates all 16 reagent panel cells at AHG, but the autocontrol and direct antiglobulin test are negative. Which is the most likely explanation?

  1. Alloantibody to a high-incidence antigen Correct answer.
  2. Warm autoantibody present in the patient's serum
  3. Rouleaux formation
  4. Cold agglutinin

Explanation

Panreactivity with a negative autocontrol suggests an alloantibody directed against a high-incidence antigen absent from the patient's own red cells. A warm autoantibody would typically produce a positive autocontrol and DAT.

Question 39Blood Banking / Immunohematology Theory and Serology

A patient with Bombay phenotype (Oh) requires transfusion. Which red cell component is compatible?

  1. Group O Rh-positive red cells
  2. Group O Rh-negative red cells
  3. Bombay phenotype (Oh) red cells Correct answer.
  4. Group A2 red cells

Explanation

Bombay phenotype red cells lack H antigen and patients have anti-H, which reacts with all normal red cells. Only Bombay phenotype red cells are compatible.

Question 40Blood Banking / Immunohematology Theory and Serology

Which laboratory method is preferred to quantify a large fetomaternal hemorrhage when the Kleihauer-Betke result is equivocal or the mother has elevated hemoglobin F?

  1. Cord blood bilirubin measurement
  2. Maternal antibody screen
  3. Direct antiglobulin test on the mother
  4. Flow cytometry for fetal hemoglobin-containing cells Correct answer.

Explanation

Flow cytometry can more accurately identify and quantify fetal red cells, especially when maternal hemoglobin F interferes with the Kleihauer-Betke test. Accurate quantification guides the dose of Rh immune globulin.

Question 41Blood Donation, Collection and Component Processing

What is the minimum acceptable hemoglobin concentration for an allogeneic whole blood donor?

  1. 12.5 g/dL Correct answer.
  2. 14.0 g/dL
  3. 13.5 g/dL
  4. 11.0 g/dL

Explanation

AABB standards require a minimum hemoglobin of 12.5 g/dL, or a hematocrit of 38%, for allogeneic blood donors. This threshold protects the donor from iron-deficiency risk and helps ensure adequate red cell mass. Values above the minimum are acceptable but do not define eligibility.

Question 42Blood Donation, Collection and Component Processing

Citrate-based anticoagulants in blood collection bags prevent clotting by binding which ion?

  1. Sodium
  2. Potassium
  3. Calcium Correct answer.
  4. Magnesium

Explanation

Citrate chelates ionized calcium, which is required for several steps in the coagulation cascade. Without free calcium, blood cannot clot in the collection bag. Sodium, potassium, and magnesium are not the ions bound by citrate.

Question 43Blood Donation, Collection and Component Processing

Whole blood-derived red cell units are stored at which temperature range?

  1. 20-24°C
  2. 1-6°C Correct answer.
  3. -18°C or colder
  4. 37°C

Explanation

Red cells are stored at 1-6°C to slow glycolysis and reduce the risk of bacterial proliferation. Frozen storage is used for plasma, and 20-24°C is used for platelets. A temperature of 37°C would accelerate metabolism and hemolysis.

Question 44Blood Donation, Collection and Component Processing

Platelet concentrates are stored under which conditions?

  1. 37°C without agitation
  2. 20-24°C with continuous agitation Correct answer.
  3. -18°C or colder
  4. 1-6°C with agitation

Explanation

Platelets require 20-24°C with continuous gentle agitation to maintain pH and oxygen delivery. Cold storage causes platelet activation and clearance, and freezing destroys platelets. A temperature of 37°C is not a storage condition.

Question 45Blood Donation, Collection and Component Processing

Fresh frozen plasma stored at -18°C or colder may be kept for up to how long?

  1. 24 hours
  2. 7 years
  3. 1 year Correct answer.
  4. 5 days

Explanation

FFP stored at -18°C or colder has a 1-year expiration. If stored at -65°C or colder, it may be kept for up to 7 years. Twenty-four hours applies after thawing, and 5 days is the storage limit for platelets.

Question 46Blood Donation, Collection and Component Processing

A whole blood collection should be completed within what maximum time to limit activation and contamination?

  1. 30 minutes
  2. 5 minutes
  3. 15 minutes Correct answer.
  4. 60 minutes

Explanation

AABB standards require whole blood collection to be completed within 15 minutes. Longer collection times increase the risk of clot formation and bacterial contamination. Five minutes is often too short for a full unit, while 30 and 60 minutes exceed the limit.

Question 47Blood Donation, Collection and Component Processing

What is the standard minimum weight for an allogeneic blood donor?

  1. 45 kg
  2. 50 kg Correct answer.
  3. 40 kg
  4. 60 kg

Explanation

The standard minimum donor weight is 50 kg (110 lb). This ensures the collected volume is a safe fraction of the donor's estimated blood volume. Weights below 50 kg require special consideration, and 60 kg is not the threshold.

Question 48Blood Donation, Collection and Component Processing

What is the minimum acceptable pH at the end of platelet storage?

  1. 7.4
  2. 6.8
  3. 6.0
  4. 6.2 Correct answer.

Explanation

AABB requires a pH of at least 6.2 at the end of the allowable platelet storage period. A lower pH indicates poor platelet metabolism and reduced viability. A pH of 7.4 is normal at collection, and 6.8 or 6.0 are not the acceptance cutoff.

Question 49Blood Donation, Collection and Component Processing

Which component is prepared by the light-spin step in the platelet-rich plasma method?

  1. Factor VIII concentrate
  2. Packed red cells
  3. Platelet-rich plasma Correct answer.
  4. Cryoprecipitate

Explanation

In the platelet-rich plasma method, a light spin separates platelet-rich plasma from red cells. A subsequent heavy spin concentrates the platelets and leaves platelet-poor plasma. Packed red cells come from the heavy spin, and cryoprecipitate is made from frozen plasma.

Question 50Blood Donation, Collection and Component Processing

A prestorage leukoreduced red cell unit must contain fewer than what number of residual white cells?

  1. 5 × 10^4
  2. 5 × 10^6 Correct answer.
  3. 1 × 10^9
  4. 5 × 10^8

Explanation

Prestorage leukoreduction must reduce white cells to fewer than 5 × 10^6 per unit. This limit reduces febrile nonhemolytic reactions and CMV transmission. A count of 5 × 10^8 is above the limit, and 1 × 10^9 is typical of unfiltered units.