Welcome to Part 44 of our Free ASCP MLS Exam Practice Questions series. This section focuses on Hematology Laboratory Techniques and Instrumentation, an essential part of laboratory practice and a frequently tested area in the ASCP MLS exam.
Modern hematology relies on both manual and automated methods, and MLS candidates must be familiar with test principles, quality assurance, and troubleshooting.
🔹 Topics Covered in This Part
- Laboratory safety and specimen handling
- Manual hematology techniques (ESR, reticulocyte count, manual differentials)
- Automated hematology analyzers: principles, operation, and interpretation
- Quality control, calibration, and troubleshooting in hematology labs
- Special stains and cytochemical methods (Wright-Giemsa, Prussian blue, myeloperoxidase, Sudan Black B)
- Flow cytometry applications in hematology
60 MCQs (3581 – 3640):
📘 How to Use These Practice Questions
- The questions in this section are designed to reinforce your understanding of lab methods, equipment, and quality practices.
- Numbering continues from the previous article — starting at Question 3581.
- Each set will be followed by answer keys and explanations for effective review.
- What is the formula to calculate an absolute cell count from a differential?
a) Number of cells counted / Total count
b) Total count / Number of cells counted
c) % of cells counted × Total count
d) % of cells counted / Total count - On a Wright-stained blood smear, a polychromatophilic red blood cell would most likely be stained by a supravital stain as a:
a) Spherocyte
b) Target cell
c) Reticulocyte
d) Sickle cell - The electrical impedance method of cell counting requires:
a) A chromogenic substrate
b) A non-conductive liquid
c) A conductive liquid
d) Two internal electrodes - Which of the following is used as a supravital stain for reticulocytes?
a) Wright stain
b) Giemsa stain
c) New methylene blue
d) Prussian blue - A manual white blood cell count is performed on a 1:20 dilution. Fifty cells are counted in the four corner squares of the hemocytometer. What is the total WBC count?
a) 2,500/µL
b) 5,000/µL
c) 7,500/µL
d) 10,000/µL - An automated hematology analyzer reports a WBC count of 10.0 x 10³/µL. Fifty nucleated red blood cells (NRBCs) are seen per 100 WBCs on the differential. What is the corrected WBC count?
a) 5,000/µL
b) 6,667/µL
c) 8,000/µL
d) 15,000/µL - If a hematology analyzer flag indicates “immature granulocytes” (IG), the next appropriate step is to:
a) Report the results as-is
b) Perform a smear review and manual differential
c) Warm the specimen to 37°C and rerun
d) Request a new sample - A falsely elevated MCHC on an automated analyzer can be caused by all of the following EXCEPT:
a) Lipemia
b) Cold agglutinins
c) Spherocytosis
d) A high reticulocyte count - The red cell distribution width (RDW) is a measure of:
a) Mean red cell hemoglobin concentration
b) Red cell size variation (anisocytosis)
c) Red cell shape variation (poikilocytosis)
d) Mean red cell volume - Which hematology analyzer technology uses multi-angle polarized scatter separation (MAPSS)?
a) Beckman Coulter
b) Sysmex
c) Abbott Cell-Dyn
d) Siemens Advia - On a Sysmex scattergram (DIFF plot), neutrophils are typically found in the area of:
a) Low side scatter and low fluorescence
b) High side scatter and low fluorescence
c) Low side scatter and high fluorescence
d) High side scatter and high fluorescence - A platelet count is performed manually. The average count in the central squares is 180 platelets. The dilution is 1:100. What is the total platelet count?
a) 180,000/µL
b) 360,000/µL
c) 720,000/µL
d) 900,000/µL - The cyanmethemoglobin method for hemoglobin measurement cannot accurately detect which form of hemoglobin?
a) Carboxyhemoglobin
b) Methemoglobin
c) Oxyhemoglobin
d) Sulfhemoglobin - Which stain is used to demonstrate the presence of iron in bone marrow stores?
a) Wright stain
b) Myeloperoxidase stain
c) Prussian blue stain
d) Sudan black B stain - The Kleihauer-Betke test is used to quantify:
a) Hemoglobin A2
b) Hemoglobin S
c) Hemoglobin F
d) Hemoglobin H - In flow cytometry, the CD5 marker is typically expressed on:
a) Mature B cells
b) Mature T cells
c) Granulocytes
d) Monocytes - Which of the following is a confirmatory test for Paroxysmal Nocturnal Hemoglobinuria (PNH)?
a) Sucrose hemolysis test
b) Flow cytometric immunophenotyping for CD55 and CD59
c) Acidified serum test (Ham test)
d) Dithionite solubility test - The stain used to identify Auer rods in leukemic blasts is:
a) Prussian blue
b) Myeloperoxidase
c) Wright-Giemsa
d) Tartrate-resistant acid phosphatase (TRAP) - Terminal deoxynucleotidyl transferase (TdT) is a marker typically found on:
a) Mature plasma cells
b) Myeloblasts
c) Lymphoblasts
d) Megakaryoblasts - A falsely prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT) in a patient with polycythemia vera is most likely due to:
a) Factor VIII deficiency
b) An excess of anticoagulant in the tube
c) The presence of a lupus anticoagulant
d) Disseminated intravascular coagulation - Which of the following will most likely cause a falsely decreased platelet count on an automated analyzer?
a) Microcytosis
b) Platelet clumping
c) Reticulocytosis
d) Spherocytosis - The principle of the hemoglobin solubility test for HbS is based on the:
a) Alkaline denaturation of hemoglobin
b) Insolubility of reduced HbS in a phosphate buffer
c) Heat precipitation of unstable hemoglobins
d) Electrophoretic mobility of hemoglobin variants - The erythrocyte sedimentation rate (ESR) can be falsely elevated by:
a) Refrigerating the specimen before testing
b) Tilting the Westergren tube
c) The presence of microclots in the sample
d) Testing the sample more than 6 hours after collection - On a Siemens Advia scattergram (Perox channel), the area representing monocytes is typically identified by:
a) High peroxidase activity and high light scatter
b) Low peroxidase activity and low light scatter
c) High peroxidase activity and low light scatter
d) Low peroxidase activity and high light scatter - A manual hematocrit determined by the microhematocrit method may be falsely elevated due to:
a) In vitro hemolysis
b) Trapped plasma
c) A short centrifugation time
d) An improperly sealed capillary tube - Which of the following stains is used to differentiate granulocytic cells from monocytic cells?
a) Prussian blue stain
b) Periodic acid-Schiff (PAS) stain
c) Nonspecific esterase stain
d) Reticulocyte stain - In a patient with a high cold agglutinin titer, the most appropriate course of action for accurate CBC results is to:
a) Dilute the sample in saline and rerun
b) Warm the sample to 37°C and rerun
c) Use a manual counting method for all parameters
d) Report the results from the initial run - The mean corpuscular volume (MCV) is calculated using which formula?
a) (Hematocrit / RBC) x 10
b) (Hemoglobin / RBC) x 10
c) (Hematocrit / Hemoglobin) x 100
d) (Hemoglobin / Hematocrit) x 100 - The presence of Heinz bodies, which are inclusions of denatured hemoglobin, can be visualized with which stain?
a) Wright stain
b) Brilliant cresyl blue supravital stain
c) Prussian blue stain
d) New methylene blue stain - The anticoagulant of choice for routine hematology testing is:
a) Sodium citrate
b) Heparin
c) EDTA
d) Potassium oxalate - The primary anticoagulant used for routine hematology testing is:
a) Sodium citrate
b) EDTA (K₂ or K₃)
c) Heparin
d) Oxalate - Excess EDTA in a blood tube may cause RBCs to appear:
a) Hypochromic
b) Spherocytic and shrunken
c) Rouleaux formation
d) Macrocytic - The principle of electrical impedance (Coulter principle) in cell counters measures:
a) Cell size and number based on resistance change
b) Optical density of hemoglobin
c) Light scatter by cytoplasmic granules
d) Fluorescent dye uptake - Flow cytometry distinguishes cell populations based on:
a) Electrical resistance
b) Light scatter and fluorescence
c) Osmotic fragility
d) Hemoglobin concentration - In a hematology analyzer, forward light scatter correlates with:
a) Cell granularity
b) Cell size
c) Nucleic acid content
d) Cytoplasmic enzyme activity - Side scatter in flow cytometry primarily reflects:
a) Cell volume
b) Granularity and internal complexity
c) Hemoglobin concentration
d) Membrane charge - Which parameter is directly measured in automated hematology analyzers?
a) Hematocrit
b) Hemoglobin concentration
c) RBC indices
d) MCHC - Hemoglobin concentration in analyzers is commonly determined using:
a) Cyanmethemoglobin method
b) Osmotic lysis test
c) ELISA
d) Immunofluorescence - The normal WBC differential is usually performed on:
a) 50 cells
b) 100 cells
c) 200 cells
d) 500 cells - The Wright–Giemsa stain is composed of:
a) Methylene blue and eosin
b) Prussian blue and safranin
c) PAS and eosin
d) Sudan black and methyl green - Which automated analyzer parameter reflects size variation of RBCs?
a) MCH
b) MCHC
c) RDW
d) MPV - Platelet clumping due to EDTA may falsely result in:
a) Pseudothrombocytopenia
b) Thrombocytosis
c) Leukopenia
d) Polycythemia - Which manual method is used to measure ESR (erythrocyte sedimentation rate)?
a) Cyanmethemoglobin method
b) Westergren method
c) Schilling test
d) Osmotic fragility test - A reticulocyte count is performed using:
a) Wright–Giemsa stain
b) Supravital stain (new methylene blue)
c) Prussian blue
d) Sudan black - Which RBC index is calculated as (Hgb × 10) / RBC count?
a) MCV
b) MCH
c) MCHC
d) RDW - Which automated analyzer principle is used for reticulocyte counts?
a) Light scatter
b) Fluorescent staining of RNA
c) Electrical impedance only
d) Osmotic lysis - The spun microhematocrit method measures:
a) Plasma hemoglobin
b) Packed RBC volume
c) Total iron stores
d) Reticulocytes - What is the main advantage of automation in hematology testing?
a) Reduces need for anticoagulants
b) Faster, accurate, and reproducible results
c) Eliminates need for staining
d) Removes operator oversight completely - Which stain is used in bone marrow cytochemistry to identify myeloblasts?
a) Myeloperoxidase (MPO)
b) PAS
c) Sudan black B
d) Both MPO and Sudan black B - Which cytochemical stain is most useful for identifying lymphoblasts?
a) PAS (Periodic acid–Schiff)
b) MPO
c) Sudan black B
d) Esterase stain - In cytochemistry, nonspecific esterase positivity indicates:
a) Myeloblasts
b) Monoblasts
c) Lymphoblasts
d) Plasma cells - The Kleihauer–Betke test detects:
a) Heinz bodies
b) Fetal hemoglobin (HbF) in RBCs
c) Iron granules
d) DNA remnants - The osmotic fragility test evaluates:
a) Platelet function
b) RBC membrane stability
c) WBC lysis resistance
d) Coagulation factor activity - Which control material is used daily to monitor hematology analyzers?
a) Normal saline
b) Commercially prepared whole blood controls
c) Distilled water
d) EDTA plasma only - Internal quality control ensures:
a) Correct test ordering
b) Accuracy and precision of test results
c) Elimination of human error
d) Calibration once per year only - External quality assurance (proficiency testing) involves:
a) Daily analyzer maintenance
b) Comparing results with reference laboratories
c) Checking patient identification
d) Using duplicate samples only - Which analyzer parameter reflects average platelet size?
a) MCHC
b) RDW
c) MPV
d) PDW - Hemoglobin electrophoresis is commonly performed at:
a) Acidic and alkaline pH
b) Alkaline pH only
c) Acidic pH only
d) Neutral pH only - Which laboratory technique is most specific for detecting gene mutations in hematology disorders?
a) Flow cytometry
b) PCR (Polymerase chain reaction)
c) Cytochemistry
d) Hemoglobin electrophoresis - Which of the following is a limitation of automated hematology analyzers?
a) Inability to detect abnormal cell morphology reliably
b) High reproducibility
c) Large test menu
d) High throughput
📌 How to Use This Practice Set
- Answer each question before checking the key.
- Focus on why the correct answer is right and the others are wrong.
- Use this set as timed practice to simulate the real exam environment.
Answer Key
Answer Key:
- c) % of cells counted × Total count
- c) Reticulocyte
- c) A conductive liquid
- c) New methylene blue
- a) 2,500/µL
- b) 6,667/µL
- b) Perform a smear review and manual differential
- d) A high reticulocyte count
- b) Red cell size variation (anisocytosis)
- c) Abbott Cell-Dyn
- b) High side scatter and low fluorescence
- a) 180,000/µL
- d) Sulfhemoglobin
- c) Prussian blue stain
- c) Hemoglobin F
- b) Mature T cells
- b) Flow cytometric immunophenotyping for CD55 and CD59
- c) Wright-Giemsa
- c) Lymphoblasts
- b) An excess of anticoagulant in the tube
- b) Platelet clumping
- b) Insolubility of reduced HbS in a phosphate buffer
- b) Tilting the Westergren tube
- d) Low peroxidase activity and high light scatter
- b) Trapped plasma
- c) Nonspecific esterase stain
- b) Warm the sample to 37°C and rerun
- a) (Hematocrit / RBC) x 10
- b) Brilliant cresyl blue supravital stain
- c) EDTA
- b) EDTA (K₂ or K₃)
- b) Spherocytic and shrunken
- a) Cell size and number based on resistance change
- b) Light scatter and fluorescence
- b) Cell size
- b) Granularity and internal complexity
- b) Hemoglobin concentration
- a) Cyanmethemoglobin method
- b) 100 cells
- a) Methylene blue and eosin
- c) RDW
- a) Pseudothrombocytopenia
- b) Westergren method
- b) Supravital stain (new methylene blue)
- b) MCH
- b) Fluorescent staining of RNA
- b) Packed RBC volume
- b) Faster, accurate, and reproducible results
- d) Both MPO and Sudan black B
- a) PAS (Periodic acid–Schiff)
- b) Monoblasts
- b) Fetal hemoglobin (HbF) in RBCs
- b) RBC membrane stability
- b) Commercially prepared whole blood controls
- b) Accuracy and precision of test results
- b) Comparing results with reference laboratories
- c) MPV
- a) Acidic and alkaline pH
- b) PCR (Polymerase chain reaction)
- a) Inability to detect abnormal cell morphology reliably
Top 8 Medical Laboratory Scientist (MLS) Exams:
Top 8 Medical Laboratory Scientist (MLS) Exams that are recognized globally and can help professionals validate their credentials and enhance their career opportunities:
1. ASCP – American Society for Clinical Pathology (USA)
- Exam Name: MLS(ASCP)
- Eligibility: Bachelor’s degree with clinical laboratory experience.
- Global Recognition: High
- Purpose: Certifies Medical Laboratory Scientists in the United States and internationally.
2. AMT – American Medical Technologists (USA)
- Exam Name: MLT(AMT) or MT(AMT)
- Eligibility: Academic and/or work experience in medical laboratory technology.
- Global Recognition: Moderate
- Purpose: Credentialing for medical technologists and technicians.
3. AIMS – Australian Institute of Medical and Clinical Scientists
- Exam Name: AIMS Certification Exam
- Eligibility: Assessment of qualifications and work experience.
- Recognition: Required for practice in Australia.
- Purpose: Certification and registration in Australia.
4. CSMLS – Canadian Society for Medical Laboratory Science
- Exam Name: CSMLS General or Subject-specific Exams
- Eligibility: Graduation from a CSMLS-accredited program or equivalent.
- Recognition: Canada
- Purpose: Entry-to-practice certification in Canada.
5. IBMS – Institute of Biomedical Science (UK)
- Exam Name: Registration and Specialist Portfolio Assessment
- Eligibility: Accredited degree and lab experience.
- Recognition: UK and some Commonwealth countries.
- Purpose: Biomedical Scientist registration with the HCPC (UK).
6. HAAD / DOH – Department of Health, Abu Dhabi (UAE)
- Exam Name: DOH/HAAD License Exam
- Eligibility: Degree in medical laboratory science and experience.
- Recognition: UAE (Abu Dhabi)
- Purpose: Licensure for medical laboratory practice in Abu Dhabi.
7. DHA – Dubai Health Authority (UAE)
- Exam Name: DHA License Exam for Medical Laboratory Technologists
- Eligibility: Relevant degree and experience.
- Recognition: Dubai, UAE
- Purpose: Professional license for clinical laboratory practice in Dubai.
8. MOH – Ministry of Health (Gulf Countries like UAE, Saudi Arabia, Kuwait)
- Exam Name: MOH License Exam
- Eligibility: BSc/Diploma in Medical Laboratory + experience.
- Recognition: Varies by country.
- Purpose: Required for practicing in public and private sector labs.
Tags:
#ASCPMLS #MLSexam #LabTech #MedicalLaboratory #BOCexam #FreePracticeQuestions #QualityControl #LaboratorySafety
