1
ASCP Recalls 2026/2027 100 Practice Questions
with Verified Answers for Medical Laboratory
Certification Preparation.
Exam Overview: This comprehensive recall bank mirrors the official ASCP Board of Certification
(BOC) Medical Laboratory Scientist (MLS) examination format. It covers the five core laboratory
disciplines: Blood Banking, Clinical Chemistry, Hematology, Microbiology, and Urinalysis/Body
Fluids. All questions are verified against current CLSI standards, ASCP BOC content outlines, and
authoritative laboratory medicine references.
DOMAIN 1: HEMATOLOGY & HEMOSTASIS (25 Questions)
Sub-Topic: Blast Cell Morphology (5 Questions)
Question 1 (Image/Cytology Identification) A Wright-Giemsa stained peripheral smear shows a
large immature cell with a high nuclear-to-cytoplasmic ratio, fine open (lacy) chromatin, and
one to multiple prominent nucleoli. The cytoplasm is basophilic and agranular. This cell is best
classified as:
A. A mature lymphocyte
B. A blast cell
C. A promyelocyte
D. A plasma cell
[CORRECT: B]
Rationale: Blast cells are characterized by a high nuclear-to-cytoplasmic ratio (N:C ratio > 4:1),
fine open (lacy/reticular) chromatin, and prominent nucleoli (1-5 visible). The cytoplasm is
typically basophilic and agranular. These morphological features distinguish blasts from more
mature cells. Mature lymphocytes (A) have condensed chromatin and scant cytoplasm;
promyelocytes (C) contain primary (azurophilic) granules; plasma cells (D) have eccentric nuclei,
clock-face chromatin, and a prominent Golgi zone. Blast identification is critical for diagnosing
acute leukemias.
Question 2 (Multiple Choice) Which combination of morphological features is MOST
characteristic of a myeloblast (AML-M1/M2) versus a lymphoblast (ALL-L1/L2)?
, 2
A. High N:C ratio + fine chromatin + no granules (seen in both)
B. Myeloblasts have finer chromatin; lymphoblasts have coarser chromatin
C. Myeloblasts may have Auer rods; lymphoblasts never have Auer rods
D. Lymphoblasts are always smaller than myeloblasts
[CORRECT: C]
Rationale: Auer rods (needle-like cytoplasmic inclusions formed from fused azurophilic
granules) are pathognomonic for myeloid lineage and are NEVER seen in lymphoblasts. Their
presence confirms AML and excludes ALL. While myeloblasts may show cytoplasmic granules or
Auer rods, lymphoblasts are agranular. Both cell types share high N:C ratios and fine chromatin
(A is true but not distinguishing). Lymphoblasts typically have coarser chromatin than
myeloblasts (B is reversed). Size overlap exists between the two (D is false). Cytochemical
staining (MPO, SBB, PAS) is required for definitive classification.
Question 3 (Select All That Apply) Which morphological features on a Wright-Giemsa stained
peripheral smear are consistent with a blast cell? (Select all that apply)
A. High nuclear-to-cytoplasmic ratio
B. Condensed, pyknotic chromatin
C. Prominent nucleoli (1-5 visible)
D. Fine, open (lacy) chromatin pattern
E. Abundant, specific (secondary) granules in cytoplasm
[CORRECT: A, C, D]
Rationale: Blast cells demonstrate: high N:C ratio (A) due to large nucleus and scant cytoplasm;
prominent nucleoli (C) indicating active ribosomal RNA synthesis for rapid proliferation; and
fine, open (lacy/reticular) chromatin (D) reflecting immature, uncondensed nuclear material.
Condensed chromatin (B) is characteristic of mature, inactive cells (lymphocytes, pyknotic
neutrophils). Specific (secondary) granules (E) appear at the myelocyte stage and beyond; blasts
lack specific granulation, though myeloblasts may contain primary (azurophilic) granules or Auer
rods.
Question 4 (Multiple Choice) A peripheral smear from a 68-year-old male shows 85% blasts
with the following features: diameter 15-20 μm, high N:C ratio, fine chromatin, 2-3 prominent
nucleoli, and basophilic cytoplasm with occasional azurophilic granules. No Auer rods are seen.
The most likely diagnosis is:
, 3
A. Acute Lymphoblastic Leukemia (ALL)
B. Acute Myeloid Leukemia (AML)
C. Chronic Myelogenous Leukemia (CML) in blast crisis
D. Hairy Cell Leukemia
[CORRECT: B]
Rationale: The presence of azurophilic granules in blasts indicates myeloid differentiation,
establishing a diagnosis of AML. While Auer rods are pathognomonic for AML, their absence
does not exclude myeloid lineage—granules alone are sufficient. ALL blasts are agranular. CML
in blast crisis (C) would show myeloid blasts but typically has a history of CML with
splenomegaly and basophilia. Hairy Cell Leukemia (D) shows mature B-cells with cytoplasmic
projections, not blasts. Flow cytometry and cytochemistry (MPO positive) would confirm AML.
Question 5 (Multiple Choice) In a bone marrow aspirate, a blast cell is identified with a
diameter of 18 μm, N:C ratio of 5:1, fine lacy chromatin, and multiple prominent nucleoli. The
cytoplasm shows no granules. Which additional test is MOST critical to determine lineage?
A. Complete Blood Count with differential
B. Myeloperoxidase (MPO) cytochemical stain
C. Iron stain (Prussian blue)
D. Reticulocyte count
[CORRECT: B]
Rationale: Myeloperoxidase (MPO) cytochemical staining is the gold standard for distinguishing
myeloid from lymphoid blasts. MPO positivity (≥3% of blasts) confirms myeloid lineage (AML);
MPO negativity supports lymphoid lineage (ALL). While flow cytometry is now standard, MPO
remains the definitive cytochemical marker per WHO classification. CBC (A) provides
quantitative data but not lineage. Iron stain (C) evaluates iron stores. Reticulocyte count (D)
assesses erythropoietic activity but does not determine blast lineage.
Sub-Topic: Corrected Reticulocyte Count (4 Questions)
Question 6 (Calculation-Based) A 45-year-old female with autoimmune hemolytic anemia has
the following results:
• Reticulocyte count: 8.0%
• Patient Hct: 24%
• Normal Hct: 45%
, 4
Calculate the Corrected Reticulocyte Count (CRC).
A. 4.3%
B. 8.0%
C. 15.0%
D. 3.2%
[CORRECT: A]
Rationale: The Corrected Reticulocyte Count formula is: CRC = Retic % × (Patient Hct / Normal
Hct). Calculation: CRC = 8.0% × () = 8.0% × 0.533 = 4.27% (rounded to 4.3%). The CRC
corrects for the degree of anemia—reticulocytes are released prematurely in severe anemia and
survive longer in circulation, artificially elevating the uncorrected percentage. A CRC > 2-3%
indicates adequate bone marrow response (hyperproliferative anemia); <2% suggests
hypoproliferative marrow (aplastic anemia, nutritional deficiency). This patient's CRC of 4.3%
confirms appropriate erythropoietic response to hemolysis.
Question 7 (Calculation-Based) A patient with sickle cell disease in crisis has:
• Reticulocyte count: 12%
• Patient Hct: 18%
• Normal Hct: 42%
What is the Corrected Reticulocyte Count, and what does it indicate about bone marrow
response?
A. 5.1% — inadequate bone marrow response
B. 5.1% — adequate bone marrow response
C. 28.0% — hyperproliferative marrow with possible marrow exhaustion
D. 12.0% — normal response for sickle cell disease
[CORRECT: B]
Rationale: CRC = 12% × (18/42) = 12% × 0.429 = 5.1%. A CRC > 2-3% indicates an adequate bone
marrow response to anemia. In sickle cell disease, chronic hemolysis drives compensatory
erythropoiesis; a CRC of 5.1% reflects robust marrow compensation. Inadequate response (A)
would show CRC <2%. The uncorrected 12% (D) overestimates true production because
reticulocytes survive longer in peripheral blood when anemia is severe. Marrow exhaustion (C)
is not supported by this adequate CRC.
ASCP Recalls 2026/2027 100 Practice Questions
with Verified Answers for Medical Laboratory
Certification Preparation.
Exam Overview: This comprehensive recall bank mirrors the official ASCP Board of Certification
(BOC) Medical Laboratory Scientist (MLS) examination format. It covers the five core laboratory
disciplines: Blood Banking, Clinical Chemistry, Hematology, Microbiology, and Urinalysis/Body
Fluids. All questions are verified against current CLSI standards, ASCP BOC content outlines, and
authoritative laboratory medicine references.
DOMAIN 1: HEMATOLOGY & HEMOSTASIS (25 Questions)
Sub-Topic: Blast Cell Morphology (5 Questions)
Question 1 (Image/Cytology Identification) A Wright-Giemsa stained peripheral smear shows a
large immature cell with a high nuclear-to-cytoplasmic ratio, fine open (lacy) chromatin, and
one to multiple prominent nucleoli. The cytoplasm is basophilic and agranular. This cell is best
classified as:
A. A mature lymphocyte
B. A blast cell
C. A promyelocyte
D. A plasma cell
[CORRECT: B]
Rationale: Blast cells are characterized by a high nuclear-to-cytoplasmic ratio (N:C ratio > 4:1),
fine open (lacy/reticular) chromatin, and prominent nucleoli (1-5 visible). The cytoplasm is
typically basophilic and agranular. These morphological features distinguish blasts from more
mature cells. Mature lymphocytes (A) have condensed chromatin and scant cytoplasm;
promyelocytes (C) contain primary (azurophilic) granules; plasma cells (D) have eccentric nuclei,
clock-face chromatin, and a prominent Golgi zone. Blast identification is critical for diagnosing
acute leukemias.
Question 2 (Multiple Choice) Which combination of morphological features is MOST
characteristic of a myeloblast (AML-M1/M2) versus a lymphoblast (ALL-L1/L2)?
, 2
A. High N:C ratio + fine chromatin + no granules (seen in both)
B. Myeloblasts have finer chromatin; lymphoblasts have coarser chromatin
C. Myeloblasts may have Auer rods; lymphoblasts never have Auer rods
D. Lymphoblasts are always smaller than myeloblasts
[CORRECT: C]
Rationale: Auer rods (needle-like cytoplasmic inclusions formed from fused azurophilic
granules) are pathognomonic for myeloid lineage and are NEVER seen in lymphoblasts. Their
presence confirms AML and excludes ALL. While myeloblasts may show cytoplasmic granules or
Auer rods, lymphoblasts are agranular. Both cell types share high N:C ratios and fine chromatin
(A is true but not distinguishing). Lymphoblasts typically have coarser chromatin than
myeloblasts (B is reversed). Size overlap exists between the two (D is false). Cytochemical
staining (MPO, SBB, PAS) is required for definitive classification.
Question 3 (Select All That Apply) Which morphological features on a Wright-Giemsa stained
peripheral smear are consistent with a blast cell? (Select all that apply)
A. High nuclear-to-cytoplasmic ratio
B. Condensed, pyknotic chromatin
C. Prominent nucleoli (1-5 visible)
D. Fine, open (lacy) chromatin pattern
E. Abundant, specific (secondary) granules in cytoplasm
[CORRECT: A, C, D]
Rationale: Blast cells demonstrate: high N:C ratio (A) due to large nucleus and scant cytoplasm;
prominent nucleoli (C) indicating active ribosomal RNA synthesis for rapid proliferation; and
fine, open (lacy/reticular) chromatin (D) reflecting immature, uncondensed nuclear material.
Condensed chromatin (B) is characteristic of mature, inactive cells (lymphocytes, pyknotic
neutrophils). Specific (secondary) granules (E) appear at the myelocyte stage and beyond; blasts
lack specific granulation, though myeloblasts may contain primary (azurophilic) granules or Auer
rods.
Question 4 (Multiple Choice) A peripheral smear from a 68-year-old male shows 85% blasts
with the following features: diameter 15-20 μm, high N:C ratio, fine chromatin, 2-3 prominent
nucleoli, and basophilic cytoplasm with occasional azurophilic granules. No Auer rods are seen.
The most likely diagnosis is:
, 3
A. Acute Lymphoblastic Leukemia (ALL)
B. Acute Myeloid Leukemia (AML)
C. Chronic Myelogenous Leukemia (CML) in blast crisis
D. Hairy Cell Leukemia
[CORRECT: B]
Rationale: The presence of azurophilic granules in blasts indicates myeloid differentiation,
establishing a diagnosis of AML. While Auer rods are pathognomonic for AML, their absence
does not exclude myeloid lineage—granules alone are sufficient. ALL blasts are agranular. CML
in blast crisis (C) would show myeloid blasts but typically has a history of CML with
splenomegaly and basophilia. Hairy Cell Leukemia (D) shows mature B-cells with cytoplasmic
projections, not blasts. Flow cytometry and cytochemistry (MPO positive) would confirm AML.
Question 5 (Multiple Choice) In a bone marrow aspirate, a blast cell is identified with a
diameter of 18 μm, N:C ratio of 5:1, fine lacy chromatin, and multiple prominent nucleoli. The
cytoplasm shows no granules. Which additional test is MOST critical to determine lineage?
A. Complete Blood Count with differential
B. Myeloperoxidase (MPO) cytochemical stain
C. Iron stain (Prussian blue)
D. Reticulocyte count
[CORRECT: B]
Rationale: Myeloperoxidase (MPO) cytochemical staining is the gold standard for distinguishing
myeloid from lymphoid blasts. MPO positivity (≥3% of blasts) confirms myeloid lineage (AML);
MPO negativity supports lymphoid lineage (ALL). While flow cytometry is now standard, MPO
remains the definitive cytochemical marker per WHO classification. CBC (A) provides
quantitative data but not lineage. Iron stain (C) evaluates iron stores. Reticulocyte count (D)
assesses erythropoietic activity but does not determine blast lineage.
Sub-Topic: Corrected Reticulocyte Count (4 Questions)
Question 6 (Calculation-Based) A 45-year-old female with autoimmune hemolytic anemia has
the following results:
• Reticulocyte count: 8.0%
• Patient Hct: 24%
• Normal Hct: 45%
, 4
Calculate the Corrected Reticulocyte Count (CRC).
A. 4.3%
B. 8.0%
C. 15.0%
D. 3.2%
[CORRECT: A]
Rationale: The Corrected Reticulocyte Count formula is: CRC = Retic % × (Patient Hct / Normal
Hct). Calculation: CRC = 8.0% × () = 8.0% × 0.533 = 4.27% (rounded to 4.3%). The CRC
corrects for the degree of anemia—reticulocytes are released prematurely in severe anemia and
survive longer in circulation, artificially elevating the uncorrected percentage. A CRC > 2-3%
indicates adequate bone marrow response (hyperproliferative anemia); <2% suggests
hypoproliferative marrow (aplastic anemia, nutritional deficiency). This patient's CRC of 4.3%
confirms appropriate erythropoietic response to hemolysis.
Question 7 (Calculation-Based) A patient with sickle cell disease in crisis has:
• Reticulocyte count: 12%
• Patient Hct: 18%
• Normal Hct: 42%
What is the Corrected Reticulocyte Count, and what does it indicate about bone marrow
response?
A. 5.1% — inadequate bone marrow response
B. 5.1% — adequate bone marrow response
C. 28.0% — hyperproliferative marrow with possible marrow exhaustion
D. 12.0% — normal response for sickle cell disease
[CORRECT: B]
Rationale: CRC = 12% × (18/42) = 12% × 0.429 = 5.1%. A CRC > 2-3% indicates an adequate bone
marrow response to anemia. In sickle cell disease, chronic hemolysis drives compensatory
erythropoiesis; a CRC of 5.1% reflects robust marrow compensation. Inadequate response (A)
would show CRC <2%. The uncorrected 12% (D) overestimates true production because
reticulocytes survive longer in peripheral blood when anemia is severe. Marrow exhaustion (C)
is not supported by this adequate CRC.
