MLT ASCP + CALIFORNIA LAW EXAMINATION
200 PRACTICE QUESTIONS WITH ANSWERS AND
RATIONALES
2026–2027 TESTING CYCLE
PART 1: ASCP MLT (ASCP) EXAMINATION (Questions 1–150)
SECTION 1: BLOOD BANKING (IMMUNOHEMATOLOGY) (Questions 1–20)
Question 1: A patient is typed as Group A, Rh(D)-negative. Which antibody is present in this
patient's serum?
Answer: Anti-B.
Rationale: A Group A individual has A antigens on their red blood cells and naturally occurring
anti-B antibodies in their serum. The patient does not have anti-A, as they have A antigens. The
Rh(D)-negative status does not affect the ABO antibodies present. Anti-B is an IgM antibody that
can cause hemolytic transfusion reactions if the patient receives group B or AB red cells.
Question 2: A patient's blood type is AB positive. Which of the following blood types can this
patient receive?
Answer: All blood types (A, B, AB, O, Rh positive or negative).
,Rationale: AB positive individuals have no antibodies against A or B antigens and no antibodies
against the Rh(D) antigen. They are the universal recipients. Type O negative is the universal
donor. While AB positive patients can receive any blood type, they should ideally receive AB
positive blood to conserve O negative units for emergencies.
Question 3: The gold standard for crossmatching blood before transfusion is:
Answer: The antiglobulin (Coombs) crossmatch.
Rationale: The antiglobulin crossmatch (also called the indirect Coombs crossmatch) detects
clinically significant unexpected antibodies in the patient's serum that could react with donor red
blood cells. It is the most sensitive crossmatch method and is required for patients with a history
of antibodies or transfusion reactions.
Question 4: A patient has a positive direct antiglobulin test (DAT). This indicates:
Answer: Antibodies are bound to the patient's red blood cells in vivo.
Rationale: A positive DAT indicates that antibodies and/or complement are bound to the
patient's red blood cells in the body. This can occur in autoimmune hemolytic anemia, hemolytic
transfusion reactions, or hemolytic disease of the newborn. The indirect antiglobulin test (IAT)
detects antibodies in the patient's serum, not on the cells.
,Question 5: The most common cause of hemolytic disease of the newborn (HDN) is:
Answer: Rh(D) incompatibility.
Rationale: Rh(D) incompatibility occurs when an Rh-negative mother carries an Rh-positive
fetus. Maternal anti-D antibodies can cross the placenta and cause hemolysis in the fetus. ABO
incompatibility can also cause HDN but is usually less severe. Kell and other antibodies can also
cause HDN but are less common.
Question 6: A patient has a positive antibody screen. The next step is:
Answer: Antibody identification using a panel of reagent red cells.
Rationale: A positive antibody screen indicates the presence of unexpected antibodies. The next
step is to identify the specific antibody(ies) using a panel of reagent red cells with known antigen
profiles. Once identified, compatible blood (negative for the corresponding antigen) must be
selected for crossmatching.
Question 7: Which of the following is a characteristic of the Rh blood group system?
Answer: Rh antigens are proteins; antibodies are typically IgG and can cause HDN.
Rationale: Rh antigens are integral membrane proteins (not carbohydrates like ABO antigens).
Rh antibodies are typically IgG and can cross the placenta, causing hemolytic disease of the
newborn. Rh antibodies are clinically significant and can cause hemolytic transfusion reactions.
, Question 8: The reagent used for Rh(D) typing is:
Answer: Anti-D serum (monoclonal or polyclonal).
Rationale: Anti-D serum is used to detect the presence of the D antigen on red blood cells.
Monoclonal anti-D reagents are commonly used. A positive reaction indicates the patient is
Rh(D)-positive; a negative reaction indicates Rh(D)-negative. Weak D testing may be required
for donors or in some patient populations.
Question 9: A patient is group O, Rh(D)-negative. Which blood type is the patient's
"compatible" red blood cell type?
Answer: O negative.
Rationale: O negative individuals have anti-A, anti-B, and anti-D (if previously sensitized)
antibodies. They can only receive O negative red blood cells. Transfusion of any other blood
type would cause a hemolytic transfusion reaction. Type O negative blood is the universal donor
and is reserved for emergencies.
Question 10: The principle of the indirect antiglobulin test (IAT) is:
Answer: Detecting antibodies in the patient's serum by incubating with reagent red cells
followed by anti-human globulin.
200 PRACTICE QUESTIONS WITH ANSWERS AND
RATIONALES
2026–2027 TESTING CYCLE
PART 1: ASCP MLT (ASCP) EXAMINATION (Questions 1–150)
SECTION 1: BLOOD BANKING (IMMUNOHEMATOLOGY) (Questions 1–20)
Question 1: A patient is typed as Group A, Rh(D)-negative. Which antibody is present in this
patient's serum?
Answer: Anti-B.
Rationale: A Group A individual has A antigens on their red blood cells and naturally occurring
anti-B antibodies in their serum. The patient does not have anti-A, as they have A antigens. The
Rh(D)-negative status does not affect the ABO antibodies present. Anti-B is an IgM antibody that
can cause hemolytic transfusion reactions if the patient receives group B or AB red cells.
Question 2: A patient's blood type is AB positive. Which of the following blood types can this
patient receive?
Answer: All blood types (A, B, AB, O, Rh positive or negative).
,Rationale: AB positive individuals have no antibodies against A or B antigens and no antibodies
against the Rh(D) antigen. They are the universal recipients. Type O negative is the universal
donor. While AB positive patients can receive any blood type, they should ideally receive AB
positive blood to conserve O negative units for emergencies.
Question 3: The gold standard for crossmatching blood before transfusion is:
Answer: The antiglobulin (Coombs) crossmatch.
Rationale: The antiglobulin crossmatch (also called the indirect Coombs crossmatch) detects
clinically significant unexpected antibodies in the patient's serum that could react with donor red
blood cells. It is the most sensitive crossmatch method and is required for patients with a history
of antibodies or transfusion reactions.
Question 4: A patient has a positive direct antiglobulin test (DAT). This indicates:
Answer: Antibodies are bound to the patient's red blood cells in vivo.
Rationale: A positive DAT indicates that antibodies and/or complement are bound to the
patient's red blood cells in the body. This can occur in autoimmune hemolytic anemia, hemolytic
transfusion reactions, or hemolytic disease of the newborn. The indirect antiglobulin test (IAT)
detects antibodies in the patient's serum, not on the cells.
,Question 5: The most common cause of hemolytic disease of the newborn (HDN) is:
Answer: Rh(D) incompatibility.
Rationale: Rh(D) incompatibility occurs when an Rh-negative mother carries an Rh-positive
fetus. Maternal anti-D antibodies can cross the placenta and cause hemolysis in the fetus. ABO
incompatibility can also cause HDN but is usually less severe. Kell and other antibodies can also
cause HDN but are less common.
Question 6: A patient has a positive antibody screen. The next step is:
Answer: Antibody identification using a panel of reagent red cells.
Rationale: A positive antibody screen indicates the presence of unexpected antibodies. The next
step is to identify the specific antibody(ies) using a panel of reagent red cells with known antigen
profiles. Once identified, compatible blood (negative for the corresponding antigen) must be
selected for crossmatching.
Question 7: Which of the following is a characteristic of the Rh blood group system?
Answer: Rh antigens are proteins; antibodies are typically IgG and can cause HDN.
Rationale: Rh antigens are integral membrane proteins (not carbohydrates like ABO antigens).
Rh antibodies are typically IgG and can cross the placenta, causing hemolytic disease of the
newborn. Rh antibodies are clinically significant and can cause hemolytic transfusion reactions.
, Question 8: The reagent used for Rh(D) typing is:
Answer: Anti-D serum (monoclonal or polyclonal).
Rationale: Anti-D serum is used to detect the presence of the D antigen on red blood cells.
Monoclonal anti-D reagents are commonly used. A positive reaction indicates the patient is
Rh(D)-positive; a negative reaction indicates Rh(D)-negative. Weak D testing may be required
for donors or in some patient populations.
Question 9: A patient is group O, Rh(D)-negative. Which blood type is the patient's
"compatible" red blood cell type?
Answer: O negative.
Rationale: O negative individuals have anti-A, anti-B, and anti-D (if previously sensitized)
antibodies. They can only receive O negative red blood cells. Transfusion of any other blood
type would cause a hemolytic transfusion reaction. Type O negative blood is the universal donor
and is reserved for emergencies.
Question 10: The principle of the indirect antiglobulin test (IAT) is:
Answer: Detecting antibodies in the patient's serum by incubating with reagent red cells
followed by anti-human globulin.
