Medical Laboratory Scientist (MLS) Examination — ASCP Board of Certification — Questions and Answers

Question 1: Which element on a laboratory requisition form is MOST critical for routing a specimen to the correct testing department?

Patient's insurance provider
Ordering physician's NPI number
Test(s) ordered and specimen type (Correct answer)
Patient's preferred language

Correct answer: Test(s) ordered and specimen type

The test ordered and specimen type determine which department receives and processes the specimen, making them the most operationally critical elements.

Question 2: The prefix 'hyper-' means:

Within normal
Above normal (Correct answer)
Without
Below normal

Correct answer: Above normal

Hyper- means above, excessive, or elevated, as in hyperglycemia or hypertension.

Question 3: Which type of pipette is most accurate for delivering an exact volume in a quantitative laboratory procedure?

Volumetric pipette (Correct answer)
Pasteur pipette
Serological pipette
Mohr pipette

Correct answer: Volumetric pipette

Volumetric (transfer) pipettes are calibrated to deliver one specific volume with the highest accuracy, making them ideal for quantitative procedures.

Question 4: An MLS notices a coworker consistently skipping the required specimen identification step before testing. The most ethical response is to:

Confront the coworker loudly in front of patients
Say nothing to avoid workplace conflict
Report the behavior to the supervisor to protect patient safety (Correct answer)
Repeat the coworker's tests personally without informing anyone

Correct answer: Report the behavior to the supervisor to protect patient safety

Patient safety supersedes workplace social comfort; unsafe practices must be reported through proper supervisory channels.

Question 5: A PT result is markedly prolonged but the PTT is normal. Which factor deficiency is most consistent with this pattern?

Factor IX
Factor VIII
Factor VII (Correct answer)
Factor XII

Correct answer: Factor VII

Factor VII is the only clotting factor unique to the extrinsic pathway; its deficiency prolongs PT while leaving PTT normal.

Question 6: A prothrombin time (PT) is reported as an INR of 3.8 for a patient on warfarin therapy. The therapeutic range for most indications is 2.0–3.0. This result should be:

Reported only if the aPTT is also prolonged
Reported as a critical value requiring immediate physician notification (Correct answer)
Reported routinely with next-day physician review
Repeated before reporting due to suspected error

Correct answer: Reported as a critical value requiring immediate physician notification

An INR of 3.8 exceeds the typical upper critical threshold (often ≥4.0 or institution-specific), and supratherapeutic anticoagulation poses bleeding risk requiring prompt clinical notification.

Question 7: When assessing a patient's arm prior to venipuncture, the MLS notices edema in the antecubital area. What is the primary concern?

Edema indicates active infection requiring glove change only
The needle may be too short to reach the vein
Edema fluid dilutes the blood sample, potentially causing falsely low results (Correct answer)
The patient may feel more discomfort than usual

Correct answer: Edema fluid dilutes the blood sample, potentially causing falsely low results

Edematous tissue contains excess interstitial fluid that can dilute the blood specimen, leading to falsely decreased analyte concentrations.

Question 8: What is the importance of staying current with trends in Emergency Procedures & Response for Medical Laboratory Scientist?

It ensures practices remain effective and relevant (Correct answer)
Trends do not affect professional practice
It is not necessary once certified
It is only required for new professionals

Correct answer: It ensures practices remain effective and relevant

Staying current with industry trends ensures that professional practices remain effective, relevant, and aligned with evolving standards.

Question 9: Which type of pipette is used for highly accurate liquid volume measurements?

Pasteur pipette
Graduated cylinder
Serological pipette
Micropipette (Correct answer)

Correct answer: Micropipette

Micropipettes are precision instruments designed for highly accurate and reproducible measurement and transfer of very small liquid volumes, typically in the microliter range. They are essential in molecular biology, clinical diagnostics, and other laboratory applications where exact volumes are critical for experimental integrity and reliable results. Their adjustable volume settings and disposable tips ensure precision and prevent cross-contamination.

Question 10: When performing a Levey-Jennings chart review, which Westgard rule is violated when one control value exceeds the mean by more than 3 standard deviations?

R-4s rejection rule
1-3s rejection rule (Correct answer)
1-2s warning rule
2-2s rejection rule

Correct answer: 1-3s rejection rule

The 1-3s rule is a rejection rule triggered when a single control value falls outside ±3 SD, indicating probable random or systematic error.

Question 11: A patient with B12 deficiency is started on intramuscular cyanocobalamin injections. Which CBC change is expected FIRST after initiating therapy?

Normalization of hemoglobin at 4 weeks
Correction of hypersegmented neutrophils
Normalization of MCV
Rise in reticulocyte count at 5–7 days (Correct answer)

Correct answer: Rise in reticulocyte count at 5–7 days

Reticulocytosis peaks at 5–7 days post-B12 injection, confirming bone marrow response before macrocytosis or hemoglobin normalize.

Question 12: A laboratory result is reported with a delta check flag. This means:

The specimen was collected in the wrong tube
The result falls outside the reference interval
The analyte is at a critical value level
The result differs significantly from the patient's previous value (Correct answer)

Correct answer: The result differs significantly from the patient's previous value

A delta check compares the current result to the patient's most recent prior result; a flag indicates a change exceeding the defined limit, alerting staff to possible error or acute clinical change.

Question 13: Which OSHA standard specifically governs laboratory worker exposure to bloodborne pathogens during emergency response?

OSHA 29 CFR 1910.1200 (Hazard Communication)
OSHA 29 CFR 1910.1030 (Bloodborne Pathogens) (Correct answer)
OSHA 29 CFR 1910.146 (Confined Spaces)
OSHA 29 CFR 1910.132 (PPE General)

Correct answer: OSHA 29 CFR 1910.1030 (Bloodborne Pathogens)

29 CFR 1910.1030 (Bloodborne Pathogens Standard) mandates exposure control plans and post-exposure procedures for laboratory settings.

Question 14: Which diagnostic test is commonly used to detect bacterial infections in the bloodstream?

Lipid Profile
Blood Culture (Correct answer)
Complete Blood Count (CBC)
Serum Electrolyte Panel

Correct answer: Blood Culture

A blood culture is the gold standard diagnostic test for detecting bacterial or fungal infections in the bloodstream, a condition known as bacteremia or septicemia. Blood samples are collected and incubated in a nutrient-rich medium to allow any present microorganisms to grow. Positive cultures can then be identified, and their susceptibility to antibiotics can be determined, guiding appropriate treatment.

Question 15: A patient refuses to provide a blood specimen. What is the FIRST action the MLS should take?

Cancel all laboratory orders for that patient
Call security to assist with the collection
Document the refusal and notify the nursing staff or ordering provider (Correct answer)
Attempt to collect the specimen while the patient is distracted

Correct answer: Document the refusal and notify the nursing staff or ordering provider

Competent adult patients have the right to refuse procedures; the refusal must be documented and the clinical team notified so patient care decisions can be made.

Question 16: Which microscopy technique uses oblique illumination to produce a three-dimensional appearance without staining, making it ideal for viewing unstained wet preparations?

Fluorescence microscopy
Phase contrast microscopy (Correct answer)
Brightfield microscopy
Darkfield microscopy

Correct answer: Phase contrast microscopy

Phase contrast microscopy converts phase shifts in light passing through transparent specimens into visible brightness changes, allowing visualization of unstained cells.

Question 17: What is the purpose of a Safety Data Sheet (SDS) in Medical Laboratory Scientist operations?

To list company policies
To provide hazard information about chemicals and materials (Correct answer)
To record financial data
To track employee schedules

Correct answer: To provide hazard information about chemicals and materials

Safety Data Sheets provide detailed information about chemical hazards, safe handling procedures, and emergency measures.

Question 18: Which of the following best describes the purpose of an ABN (Advance Beneficiary Notice) in laboratory documentation?

It records the chain of custody for forensic specimens
It authorizes the laboratory to perform STAT testing
It documents patient consent for an invasive procedure
It notifies Medicare patients that a test may not be covered and they may be billed (Correct answer)

Correct answer: It notifies Medicare patients that a test may not be covered and they may be billed

An ABN informs Medicare beneficiaries that a specific test may not be covered and that they will be personally responsible for the cost if Medicare denies the claim.

Question 19: A urine dipstick is positive for blood, but microscopy shows no red blood cells. The most likely explanation is:

White cell casts in the specimen
Myoglobinuria or hemoglobinuria (Correct answer)
Contamination with vaginal flora
Increased urinary bilirubin

Correct answer: Myoglobinuria or hemoglobinuria

The dipstick peroxidase reaction detects heme, so both free hemoglobin (hemoglobinuria) and myoglobin (myoglobinuria) produce a positive result in the absence of intact RBCs.

Question 20: Which of the following tests is used to diagnose tuberculosis (TB)?

Mantoux Tuberculin Skin Test (TST) (Correct answer)
Hematocrit Test
D-dimer Test
Rapid Strep Test

Correct answer: Mantoux Tuberculin Skin Test (TST)

The Mantoux Tuberculin Skin Test (TST), also known as a PPD test, is a common diagnostic tool used to screen for latent tuberculosis infection. It involves injecting a small amount of tuberculin purified protein derivative (PPD) into the forearm. A localized immune reaction (induration) observed after 48-72 hours indicates exposure to Mycobacterium tuberculosis, though further tests are needed to confirm active disease.

Question 21: What is the primary reason for using a standardized format when reporting laboratory test results?

To reduce the time required for reporting
To allow patients to interpret results on their own
To ensure consistency and accuracy (Correct answer)
To increase the number of tests ordered

Correct answer: To ensure consistency and accuracy

Using a standardized format for reporting laboratory test results is crucial to ensure consistency and accuracy across different healthcare settings and providers. This standardization minimizes misinterpretation, reduces the likelihood of errors, and allows for clear, unambiguous communication of vital patient information. Ultimately, it enhances patient safety and supports effective clinical decision-making.

Question 22: What does PPE stand for in the context of Medical Laboratory Scientist safety protocols?

Public Policy Enforcement
Professional Performance Evaluation
Project Planning Essentials
Personal Protective Equipment (Correct answer)

Correct answer: Personal Protective Equipment

PPE stands for Personal Protective Equipment, which includes items worn to minimize exposure to hazards that cause injuries.

Question 23: When reviewing a patient's medical record prior to phlebotomy, the MLS notes the patient is on warfarin. What is the primary concern for specimen collection?

Warfarin invalidates all coagulation test results
The anticoagulant may interfere with CBC tube selection
Prolonged bleeding after venipuncture requires extended pressure time (Correct answer)
A special transport medium is required for the specimen

Correct answer: Prolonged bleeding after venipuncture requires extended pressure time

Patients on warfarin have prolonged clotting times, so extended pressure must be applied after venipuncture to achieve hemostasis.

Question 24: How does collaboration enhance Emergency Procedures & Response in Medical Laboratory Scientist?

It brings diverse perspectives and improves outcomes (Correct answer)
It reduces individual accountability
It creates unnecessary meetings
It slows down the process

Correct answer: It brings diverse perspectives and improves outcomes

Collaboration brings together different viewpoints and expertise, leading to better decision-making and outcomes.

Question 25: A CSF specimen is received with xanthochromia. This finding is most suggestive of:

Bacterial meningitis
Traumatic tap
Subarachnoid hemorrhage that occurred hours to days ago (Correct answer)
Viral encephalitis

Correct answer: Subarachnoid hemorrhage that occurred hours to days ago

Xanthochromia (yellow discoloration) results from oxyhemoglobin and bilirubin released after red cell lysis and is a hallmark of subarachnoid hemorrhage, typically appearing 2–4 hours after the bleed.

Question 26: What is a risk register in Medical Laboratory Scientist practice?

An employee directory
A sign-in sheet for safety meetings
A documented list of identified risks with their analysis and response plans (Correct answer)
A financial ledger

Correct answer: A documented list of identified risks with their analysis and response plans

A risk register is a document that records all identified risks, their assessment, and planned responses for tracking and management.

Question 27: A requisition is received for a drug level with no dose or last dose time listed. Why is this information critical?

It is needed for billing purposes under ICD-10 coding
It is required only for controlled substances by federal law
Trough vs. peak timing affects therapeutic range interpretation (Correct answer)
It determines which tube color to use for collection

Correct answer: Trough vs. peak timing affects therapeutic range interpretation

Knowing the last dose time determines whether a specimen is a trough or peak level, which directly affects whether the drug concentration is within therapeutic range.

Question 28: In Medical Laboratory Scientist, what is the purpose of team-building activities?

To waste time during work hours
To strengthen collaboration, trust, and communication (Correct answer)
To identify the weakest team member
To comply with HR requirements

Correct answer: To strengthen collaboration, trust, and communication

Team-building activities enhance collaboration, build trust among team members, and improve communication skills.

Question 29: Which approach best supports quality outcomes in Clinical Procedures & Protocols for Medical Laboratory Scientist?

Rushing through tasks
Avoiding quality checks
Relying solely on intuition
Systematic application of evidence-based methods (Correct answer)

Correct answer: Systematic application of evidence-based methods

Evidence-based methods provide a reliable foundation for achieving consistent, high-quality outcomes.

Question 30: A patient with acute promyelocytic leukemia (APL) is started on ATRA therapy. Which potentially fatal complication should be monitored with daily CBC and coagulation studies?

Differentiation syndrome and DIC (Correct answer)
Capillary leak syndrome and hypoalbuminemia
Tumor lysis syndrome and hyperkalemia
Aplastic crisis and agranulocytosis

Correct answer: Differentiation syndrome and DIC

APL carries high risk of DIC from granule release, and ATRA differentiation syndrome (respiratory distress, fever, effusions) can be fatal; both require vigilant lab monitoring.

Question 31: Which type of quality control material is most appropriate for monitoring day-to-day analytical performance on a chemistry analyzer?

Pooled patient sera without assigned values
Calibrators provided by the manufacturer
Patient samples from the previous day
Commercially prepared assayed controls with known target values (Correct answer)

Correct answer: Commercially prepared assayed controls with known target values

Commercially prepared assayed controls with established target ranges allow objective monitoring of analytical performance against known values.

Question 32: An antibody identification panel in the blood bank is primarily used to:

Screen donor blood for infectious disease markers
Identify the specificity of unexpected antibodies in patient serum (Correct answer)
Assess platelet function before transfusion
Confirm a patient's ABO and Rh blood type

Correct answer: Identify the specificity of unexpected antibodies in patient serum

An antibody identification panel uses a set of reagent red cells with known antigen profiles to determine the specificity of an unexpected antibody detected in the patient's serum or plasma.

Question 33: What does the term 'resolution' refer to when describing a centrifuge's performance?

Temperature control accuracy
Ability to separate two particles of different sedimentation rates (Correct answer)
Volume capacity of the rotor
Maximum RPM achievable

Correct answer: Ability to separate two particles of different sedimentation rates

Resolution in centrifugation refers to how well the instrument can separate two populations of particles with different densities or sizes.

Question 34: What is a fundamental principle of Clinical Procedures & Protocols in Medical Laboratory Scientist practice?

Using outdated methods
Following established standards and best practices (Correct answer)
Ignoring industry guidelines
Working in isolation without guidance

Correct answer: Following established standards and best practices

Following established standards and best practices ensures quality and consistency in Clinical Procedures & Protocols.

Question 35: A hemoglobin electrophoresis at alkaline pH shows a band migrating to the S position. Which confirmatory test best differentiates HbS from HbD?

Acid electrophoresis (pH 6.2) (Correct answer)
Reticulocyte count
Heinz body preparation
Osmotic fragility test

Correct answer: Acid electrophoresis (pH 6.2)

Acid electrophoresis separates HbS from HbD because HbD migrates with HbA at acid pH while HbS remains in the S position, confirming the identity of the variant.

Question 36: A fasting glucose specimen is received, but the requisition does not indicate fasting status. What is the appropriate course of action?

Reject the specimen and order a recollection with fasting documentation
Add a comment 'fasting status unknown' only if glucose is elevated
Contact the patient or nursing unit to verify fasting status before reporting (Correct answer)
Run the specimen and report results as non-fasting

Correct answer: Contact the patient or nursing unit to verify fasting status before reporting

Fasting status must be verified and documented because it directly affects the interpretation of fasting glucose results.

Question 37: A patient with chronic kidney disease (CKD stage 4) has a hemoglobin of 9.2 g/dL and serum ferritin of 180 ng/mL with transferrin saturation of 18%. The treatment of choice is:

IV iron supplementation followed by reassessment (Correct answer)
Oral iron supplementation alone
Red blood cell transfusion
Erythropoiesis-stimulating agent (ESA) without iron

Correct answer: IV iron supplementation followed by reassessment

TSAT below 20% in CKD anemia indicates functional iron deficiency; IV iron is preferred over oral due to impaired GI absorption and superior bioavailability.

Question 38: A patient with hemophilia A has a factor VIII level of 2% and is scheduled for major surgery. What pre-operative factor VIII target level should be achieved?

Greater than 150% to account for consumption
80–100% (Correct answer)
25–50%
50–80%

Correct answer: 80–100%

For major surgery in hemophilia A, factor VIII levels should be raised to 80–100% pre-operatively and maintained above 50% post-operatively per World Federation of Hemophilia guidelines.

Question 39: Which risk response strategy involves transferring risk to a third party in Medical Laboratory Scientist?

Acceptance
Avoidance
Mitigation
Transfer (e.g., insurance) (Correct answer)

Correct answer: Transfer (e.g., insurance)

Risk transfer shifts the financial or operational impact of a risk to another party, commonly through insurance or contracts.

Question 40: When performing a manual differential on a peripheral blood smear, the MLS should count cells in which area of the smear?

The center of the smear regardless of cell distribution
The monolayer area where RBCs just touch or slightly overlap (Correct answer)
The thick area near the feathered edge where cells overlap
The feathered edge where cells are most spread

Correct answer: The monolayer area where RBCs just touch or slightly overlap

The monolayer (counting area) is where RBCs are evenly distributed and just touching, providing accurate morphology and an unbiased differential count.

Question 41: A laboratory uses a 1:10 dilution of a sample. If the original concentration is 500 mg/dL, what is the concentration in the diluted sample?

5 mg/dL
250 mg/dL
50 mg/dL (Correct answer)
100 mg/dL

Correct answer: 50 mg/dL

A 1:10 dilution reduces the concentration by a factor of 10; 500 mg/dL ÷ 10 = 50 mg/dL in the diluted sample.

Question 42: An MLS is asked by a friend to look up a mutual acquaintance's recent lab results 'just out of curiosity.' The MLS should:

Access only the most recent result to minimize the breach
Share the results if the acquaintance is also a healthcare worker
Look up the results but not share them with others
Decline; accessing records without a treatment purpose violates patient privacy (Correct answer)

Correct answer: Decline; accessing records without a treatment purpose violates patient privacy

Accessing patient records without a legitimate clinical reason is a HIPAA violation regardless of personal relationships.

Question 43: Which of the following BEST describes 'total allowable error' (TEa)?

The difference between two method means
The maximum permissible combination of bias and imprecision for an analyte (Correct answer)
The acceptable range for proficiency testing scores
The sum of all QC failures in a month

Correct answer: The maximum permissible combination of bias and imprecision for an analyte

TEa defines the maximum error a method can produce and still yield clinically acceptable results, incorporating both systematic bias and random imprecision.

Question 44: Which of the following infectious waste categories requires incineration or steam sterilization before disposal in a sanitary landfill?

Urine specimens in sealed plastic containers
Pathological waste including tissues and body parts (Correct answer)
Expired reagents with no infectious material
Routine blood collection tubes that are intact

Correct answer: Pathological waste including tissues and body parts

Pathological waste (tissues, body parts, blood) must be treated by incineration or autoclaving before landfill disposal per state and federal regulations.

Question 45: A blood culture flags positive after 18 hours of incubation. Gram stain shows gram-positive diplococci. Most likely organism in an adult with meningitis is:

Haemophilus influenzae
Listeria monocytogenes
Streptococcus pneumoniae (Correct answer)
Neisseria meningitidis

Correct answer: Streptococcus pneumoniae

S. pneumoniae appears as lancet-shaped gram-positive diplococci and is the leading cause of bacterial meningitis in adults; Neisseria is gram-negative.

Question 46: A laboratory's glucose method has a sigma value of 6. This indicates:

Calibration must occur every 6 hours
Six QC failures occurred in the past month
The method requires intensive QC monitoring
The method performs near six sigma and needs minimal QC rules (Correct answer)

Correct answer: The method performs near six sigma and needs minimal QC rules

A sigma value of 6 indicates excellent analytical performance (TEa is 6 SD wide), allowing simplified QC protocols with fewer control measurements.

Question 47: A positive DAT (direct antiglobulin test) with anti-IgG reagent, combined with a negative DAT with anti-C3d, is most consistent with:

Drug-induced immune hemolytic anemia or warm autoimmune hemolytic anemia (Correct answer)
Paroxysmal cold hemoglobinuria
Hemolytic disease of the fetus and newborn
Cold agglutinin disease

Correct answer: Drug-induced immune hemolytic anemia or warm autoimmune hemolytic anemia

Warm AIHA and many drug-induced cases coat red cells with IgG without complement deposition, producing a positive anti-IgG DAT and negative anti-C3d DAT.

Question 48: Which skill is most important for success in Emergency Procedures & Response within Medical Laboratory Scientist?

Continuous learning and adaptation (Correct answer)
Resisting change
Avoiding feedback
Working without any training

Correct answer: Continuous learning and adaptation

Continuous learning ensures professionals stay current with evolving practices in Emergency Procedures & Response.

Question 49: A laboratory worker sustains a needlestick injury from a patient known to be HIV-positive. Which action should be taken FIRST?

Wash the wound thoroughly with soap and water (Correct answer)
Report immediately to employee health
Begin post-exposure prophylaxis within 2 hours
Draw blood from the source patient for baseline testing

Correct answer: Wash the wound thoroughly with soap and water

Immediate wound washing with soap and water is the first step to reduce the inoculum before any reporting or treatment.

Question 50: An MLS must dispose of sharps contaminated with a chemotherapy drug (e.g., methotrexate-contaminated needles). Which disposal container is correct?

Black hazardous pharmaceutical waste container
Standard red biohazard sharps container
Yellow chemotherapy (chemo) waste sharps container (Correct answer)
Regular puncture-resistant container without biohazard labeling

Correct answer: Yellow chemotherapy (chemo) waste sharps container

Chemotherapy-contaminated sharps require a yellow chemotherapy waste container to ensure proper tracking, segregation, and disposal under RCRA regulations.

Question 51: Which action is REQUIRED when a laboratory's QC fails and patient results have already been reported?

Immediately cancel all pending orders
Inform only the billing department
Investigate the failure, notify the medical director, and consider recalling affected results (Correct answer)
Rerun QC until it passes and document the passing result only

Correct answer: Investigate the failure, notify the medical director, and consider recalling affected results

A retrospective QC failure requires root cause investigation, medical director notification, and assessment of whether reported patient results were clinically impacted.

Question 52: After an accidental needlestick exposure to HIV-positive blood, when should post-exposure prophylaxis (PEP) ideally be initiated?

Within 72 hours of exposure
Within 24 hours of exposure
Immediately within 2 hours, but no later than 72 hours (Correct answer)
Within 1 week of exposure

Correct answer: Immediately within 2 hours, but no later than 72 hours

PEP is most effective when started within 2 hours; it must be initiated no later than 72 hours after exposure to be beneficial.

Question 53: Which diagnostic imaging technique is commonly used to visualize soft tissue structures such as the liver, kidneys, and heart?

Ultrasound (Correct answer)
MRI
X-ray
CT Scan

Correct answer: Ultrasound

Ultrasound imaging uses high-frequency sound waves to create real-time images of internal body structures. It is particularly effective for visualizing soft tissues and organs like the liver, kidneys, and heart because sound waves reflect differently off various tissue densities. Unlike X-rays, it does not use ionizing radiation and can show movement, blood flow, and organ function dynamically, making it a versatile and safe diagnostic tool.

Question 54: A patient's serum creatinine is 1.1 mg/dL. The estimated GFR (eGFR) calculated using the CKD-EPI equation is 68 mL/min/1.73m². This result best reflects:

Mildly to moderately decreased kidney function (eGFR 45–89)
Moderately decreased kidney function (eGFR 30–59)
Mildly decreased kidney function (eGFR 60–89) (Correct answer)
Normal kidney function (eGFR ≥90)

Correct answer: Mildly decreased kidney function (eGFR 60–89)

An eGFR of 68 mL/min/1.73m² falls in the G2 CKD category (60–89), indicating mildly decreased kidney function; normal is ≥90 mL/min/1.73m².

Question 55: In a biosafety cabinet Class II Type A2, the percentage of air recirculated within the cabinet versus exhausted is approximately:

70% recirculated, 30% exhausted (Correct answer)
30% recirculated, 70% exhausted
50% recirculated, 50% exhausted
100% recirculated, 0% exhausted

Correct answer: 70% recirculated, 30% exhausted

Class II Type A2 BSCs recirculate approximately 70% of air through HEPA filters and exhaust about 30% to the environment (via HEPA or hard-duct).

Question 56: Which of the following organisms requires both an alkaline (pH 8.6) peptone water enrichment and TCBS agar for optimal isolation from stool?

Shigella sonnei
Campylobacter jejuni
Yersinia enterocolitica
Vibrio cholerae (Correct answer)

Correct answer: Vibrio cholerae

Vibrio cholerae grows optimally in alkaline conditions; alkaline peptone water enrichment followed by plating on TCBS (thiosulfate-citrate-bile salts-sucrose) agar is the standard isolation method.

Question 57: Which documentation is MOST critical to include when reporting a critical (panic) value?

The patient's insurance information and attending physician's name
The instrument ID and reagent lot number used for the test
The time the result was reviewed by a supervisor
The name of the person notified, time of notification, and value reported (Correct answer)

Correct answer: The name of the person notified, time of notification, and value reported

Critical value documentation must include who was notified, the time of notification, and the value reported to ensure a complete audit trail.

Question 58: A patient with CML on imatinib therapy achieves a major molecular response (BCR-ABL1 IS ≤0.1%). The monitoring frequency recommendation changes to:

Annual cytogenetics only
Monthly PCR for BCR-ABL1 indefinitely
Every 3–6 months PCR for BCR-ABL1 (Correct answer)
Discontinue monitoring after 12 months of response

Correct answer: Every 3–6 months PCR for BCR-ABL1

Once major molecular response is confirmed, international guidelines recommend BCR-ABL1 PCR monitoring every 3–6 months to detect loss of response early.

Question 59: Which laboratory test is used to MONITOR patients receiving thiopurine therapy (azathioprine or 6-mercaptopurine) for inflammatory bowel disease?

Serum drug level by immunoassay
Erythrocyte sedimentation rate
CBC and liver function tests only
Thiopurine methyltransferase (TPMT) activity and thiopurine metabolite levels (Correct answer)

Correct answer: Thiopurine methyltransferase (TPMT) activity and thiopurine metabolite levels

TPMT genotype/phenotype guides dosing, while 6-TGN and 6-MMP metabolite levels help optimize efficacy and identify toxicity or non-adherence.

Question 60: Which quality control rule is violated when two consecutive QC values fall more than 2 standard deviations from the mean on the same side?

Westgard 1-3s rule
Westgard 1-2s warning rule
Westgard R-4s rule
Westgard 2-2s rule (Correct answer)

Correct answer: Westgard 2-2s rule

The 2-2s rule is violated when two consecutive controls exceed ±2 SD in the same direction, signaling a systematic error.

Question 61: In flow cytometry, the Forward Scatter (FSC) parameter primarily correlates with which cell property?

Cell surface antigen expression
Cell size (volume) (Correct answer)
Internal complexity/granularity
Mitochondrial activity

Correct answer: Cell size (volume)

Forward scatter (FSC) measures light diffracted around the cell and correlates with cell size, while side scatter (SSC) correlates with internal granularity.

Question 62: What is the importance of staying current with trends in Medical Terminology & Anatomy for Medical Laboratory Scientist?

It ensures practices remain effective and relevant (Correct answer)
Trends do not affect professional practice
It is not necessary once certified
It is only required for new professionals

Correct answer: It ensures practices remain effective and relevant

Staying current with industry trends ensures that professional practices remain effective, relevant, and aligned with evolving standards.

Question 63: In the event of an earthquake during a laboratory shift, what action should MLS personnel take if unable to evacuate?

Stand in a doorframe for structural protection
Drop to the floor, take cover under a sturdy surface, and hold on (Correct answer)
Attempt to secure open chemical containers before taking cover
Run to the nearest exit immediately during shaking

Correct answer: Drop to the floor, take cover under a sturdy surface, and hold on

Drop, Cover, and Hold On is the evidence-based earthquake response protocol, as doorframes offer no special protection in modern buildings.

Question 64: When assessing a patient for a glucose tolerance test (GTT), which pre-test instruction is MOST important to verify?

That the patient took insulin within 2 hours of the test
That the patient consumed a high-carbohydrate meal the night before
That the patient avoided caffeine for 24 hours
That the patient fasted for 8–12 hours and avoided strenuous exercise (Correct answer)

Correct answer: That the patient fasted for 8–12 hours and avoided strenuous exercise

An 8–12 hour fast and avoidance of strenuous exercise are essential preconditions for a valid GTT, as both can significantly alter glucose metabolism.

Question 65: Which piece of laboratory equipment is used to measure the absorbance of a solution at a specific wavelength?

Pipette
Centrifuge
Spectrophotometer (Correct answer)
Microscope

Correct answer: Spectrophotometer

A spectrophotometer is an analytical instrument used to measure the intensity of light absorbed or transmitted by a solution at specific wavelengths. It quantifies the amount of light absorbed, which is directly proportional to the concentration of the analyte in the solution, according to Beer-Lambert's Law. This makes it essential for various quantitative assays in a clinical laboratory, such as measuring enzyme activity or analyte concentrations.

Question 66: Which of the following best describes the purpose of a 'delta check' in laboratory testing?

Comparing current patient result to a previous result from the same patient (Correct answer)
Comparing current result to a QC control value
Verifying instrument calibration against a standard
Checking for interfering substances in the sample

Correct answer: Comparing current patient result to a previous result from the same patient

A delta check flags when a patient's current result differs significantly from their previous result, helping detect specimen misidentification or acute patient changes.

Question 67: A critical value for serum potassium is reported to the nurse. The nurse is unavailable. What is the correct next step?

File the result and let the physician see it on rounds
Leave a voicemail and document the attempt
Wait 30 minutes and call again
Contact the charge nurse or covering physician and document (Correct answer)

Correct answer: Contact the charge nurse or covering physician and document

Critical values must be communicated to a responsible caregiver immediately; if the primary nurse is unavailable, the charge nurse or covering provider must be notified and all attempts documented.

Question 68: A laboratory's glucose linearity study shows acceptable results from 10–500 mg/dL but not above. What should be done for patient samples with glucose above 500 mg/dL?

Repeat the test twice and average the results
Dilute the sample and multiply the result by the dilution factor (Correct answer)
Use a different reagent lot that may have higher linearity
Report the result with a 'greater than' symbol without dilution

Correct answer: Dilute the sample and multiply the result by the dilution factor

Samples exceeding the analytical measurement range must be diluted; results are then multiplied by the dilution factor to report an accurate value.

Question 69: Which transfusion reaction presents with fever, chills, and rigors within 1–6 hours post-transfusion without evidence of hemolysis?

Febrile non-hemolytic transfusion reaction (FNHTR) (Correct answer)
Acute hemolytic transfusion reaction
Transfusion-associated circulatory overload (TACO)
Allergic/urticarial reaction

Correct answer: Febrile non-hemolytic transfusion reaction (FNHTR)

FNHTR is caused by recipient antibodies against donor leukocyte HLA antigens or by cytokines that accumulate in stored blood products, producing fever without red cell destruction.

Question 70: A patient with iron deficiency anemia is prescribed oral ferrous sulfate. Which laboratory parameter is the BEST indicator of early treatment response?

Serum ferritin
Reticulocyte count (Correct answer)
Mean corpuscular volume
Hemoglobin level

Correct answer: Reticulocyte count

Reticulocyte count rises within 3–5 days of starting iron therapy, making it the earliest measurable response to treatment.

Question 71: Which component of patient documentation is most important when an MLS performs a corrected report after releasing erroneous results?

Rerunning the specimen on a different analyzer without notation
Issuing a corrected report that references the original incorrect report with the reason for correction (Correct answer)
Verbally notifying only the ordering physician without written documentation
Deleting the original report from the electronic system

Correct answer: Issuing a corrected report that references the original incorrect report with the reason for correction

A corrected report must reference the original incorrect report, state the reason for correction, and be clearly labeled as corrected to maintain a complete and transparent audit trail.

Question 72: Which quality control material is used to verify that a laboratory test is performing correctly at a concentration near the medical decision level?

Calibrator
Reagent blank
Control material (QC) (Correct answer)
Reference material

Correct answer: Control material (QC)

Control materials are independent samples with known (or target) values run alongside patient samples to monitor ongoing assay performance.

Question 73: What is the first step in the risk management process for Medical Laboratory Scientist?

Writing a risk report
Identifying potential risks and hazards (Correct answer)
Transferring risk to insurance
Implementing controls immediately

Correct answer: Identifying potential risks and hazards

Risk identification is the first step, as you must know what risks exist before you can assess and manage them.

Question 74: An MLS receives a requisition with illegible handwriting for the test ordered. What should be done?

Return the requisition to the nursing station without action
Make an educated guess based on the diagnosis listed
Perform the most common test for that diagnosis
Contact the ordering clinician for clarification before processing (Correct answer)

Correct answer: Contact the ordering clinician for clarification before processing

Illegible orders must be clarified with the ordering clinician to prevent errors and ensure the correct test is performed.

Question 75: A patient's electronic order requires a 'timed specimen' for cortisol at 0800. The MLS collects the specimen at 0830. What is the correct action?

Document the actual collection time as 0830 and notify the provider of the delay (Correct answer)
Change the documented time to 0800 to match the order
Discard the specimen and collect a new one the following morning
Process the specimen without documenting the time discrepancy

Correct answer: Document the actual collection time as 0830 and notify the provider of the delay

The actual collection time must always be documented accurately; the provider should be notified of the 30-minute delay so they can determine if the result is still clinically useful.

Question 76: Which assessment finding should prompt the MLS to select an alternative collection site during phlebotomy?

A faint scar from a previous venipuncture
A mastectomy on the ipsilateral side of the intended draw arm (Correct answer)
Patient preference for the left arm
Patient anxiety about the procedure

Correct answer: A mastectomy on the ipsilateral side of the intended draw arm

Venipuncture on the same side as a mastectomy risks lymphedema and inaccurate results due to altered lymphatic drainage and should be avoided.

Question 77: During a chemical emergency, MSDS/SDS documentation is critical. Where must SDS sheets be immediately accessible to laboratory workers?

In the department manager's office only
On the facility intranet, accessible only from administrative computers
At the hospital security desk for emergency personnel
In the work area where chemicals are used or stored (Correct answer)

Correct answer: In the work area where chemicals are used or stored

OSHA requires SDS to be readily accessible to employees in their work area during each work shift.

Question 78: A patient with type 2 diabetes has an HbA1c of 9.8%. After 3 months of metformin therapy, repeat HbA1c is 9.1%. This result MOST likely indicates:

Hemoglobin variant interfering with the assay
Treatment failure requiring insulin initiation
Adequate glycemic control achieved
Partial response; consider adding a second agent (Correct answer)

Correct answer: Partial response; consider adding a second agent

A 0.7% reduction with HbA1c still well above the 7% target suggests a partial response, supporting addition of a second antidiabetic agent.

Question 79: At what temperature and conditions must platelets be stored in the blood bank?

4°C with intermittent agitation
−18°C or colder
1–6°C with no agitation
20–24°C with continuous gentle agitation (Correct answer)

Correct answer: 20–24°C with continuous gentle agitation

Platelets must be stored at 20–24°C with continuous gentle agitation to maintain metabolic activity, pH, and prevent platelet clumping.

Question 80: A laboratory receives a suspicious package that may contain a biological agent. What is the correct immediate response?

Open the package under a biosafety cabinet to assess contents
Isolate the package, evacuate the area, and contact security and local authorities (Correct answer)
Shake the package to listen for liquid contents before deciding next steps
Place the package in an autoclave to neutralize any potential pathogen

Correct answer: Isolate the package, evacuate the area, and contact security and local authorities

Isolation and evacuation limit potential exposure while authorities trained in hazmat response assess and manage the threat.

Question 81: An MLS drops a large container of liquid nitrogen in the laboratory. What is the primary hazard of this event?

Cryogenic burns and rapid oxygen depletion causing asphyxiation risk (Correct answer)
Explosive chemical reaction with water on the laboratory floor
Extreme frostbite hazard only, with no airborne exposure concerns
Hydrogen cyanide gas production from the nitrogen reacting with organic matter

Correct answer: Cryogenic burns and rapid oxygen depletion causing asphyxiation risk

Liquid nitrogen rapidly vaporizes into nitrogen gas, displacing oxygen and creating an asphyxiation risk in addition to causing severe cryogenic contact injuries.

Question 82: Cryoprecipitate is the blood product of choice for providing which coagulation factors?

Factors XI, XII, and prekallikrein
Factors VII, IX, and X
Factor VIII, Factor XIII, fibrinogen, and von Willebrand factor (Correct answer)
Factors II, V, IX, and X (prothrombin complex)

Correct answer: Factor VIII, Factor XIII, fibrinogen, and von Willebrand factor

Cryoprecipitate is prepared from the cold-insoluble portion of FFP and is concentrated in Factor VIII, Factor XIII, fibrinogen, and von Willebrand factor, making it useful in hemophilia A, vWD, and hypofibrinogenemia.

Question 83: Which safety symbol on a chemical label indicates that the substance is flammable?

Flame symbol alone (Correct answer)
Flame symbol over a circle (oxidizer)
Exclamation mark (!) in a diamond
Skull and crossbones

Correct answer: Flame symbol alone

The GHS flame pictogram (flame symbol without circle) indicates flammable liquids, gases, or solids; the flame over a circle indicates oxidizers.

Question 84: During capillary blood collection, why should the first drop of blood be wiped away?

It may be contaminated with tissue fluid that dilutes the sample (Correct answer)
It contains too many platelets
It has higher oxygen content
It clots faster than subsequent drops

Correct answer: It may be contaminated with tissue fluid that dilutes the sample

The first drop may contain interstitial (tissue) fluid from the puncture, which dilutes the blood sample and can alter analyte results.

Question 85: Which immunoglobulin class is produced first during a primary immune response and is the predominant antibody detected in ABO blood grouping (back type)?

IgA
IgG
IgE
IgM (Correct answer)

Correct answer: IgM

IgM is the first antibody produced in a primary immune response and is the class responsible for naturally occurring ABO antibodies (anti-A and anti-B) detected in the reverse (back) type.

Question 86: Which blood type is the universal recipient for packed red blood cells?

O positive
B positive
A positive
AB positive (Correct answer)

Correct answer: AB positive

AB positive individuals have A, B, and D antigens on their red cells and no ABO antibodies in serum, allowing them to receive red cells from any ABO/Rh blood group.

Question 87: Which coagulation test result pattern is most consistent with disseminated intravascular coagulation (DIC)?

Normal PT, normal aPTT, decreased fibrinogen, negative D-dimer
Prolonged PT, prolonged aPTT, decreased fibrinogen, elevated D-dimer (Correct answer)
Prolonged PT, normal aPTT, elevated fibrinogen, negative D-dimer
Normal PT, prolonged aPTT, normal fibrinogen, negative D-dimer

Correct answer: Prolonged PT, prolonged aPTT, decreased fibrinogen, elevated D-dimer

DIC consumes clotting factors and platelets while activating fibrinolysis, resulting in prolonged PT and aPTT, low fibrinogen, and markedly elevated D-dimer.

Question 88: Which test is most appropriate for diagnosing diabetes mellitus?

Oral Glucose Tolerance Test (OGTT)
Fasting Blood Sugar (FBS)
Hemoglobin A1c (Correct answer)
Random Blood Glucose (RBG)

Correct answer: Hemoglobin A1c

The Hemoglobin A1c test measures the average blood glucose levels over the past two to three months by quantifying the percentage of hemoglobin in red blood cells that is glycated. This provides a long-term picture of glucose control, making it a highly effective and widely used diagnostic tool for diabetes mellitus. Unlike single-point glucose measurements, A1c is not affected by recent food intake and offers a more stable indicator of chronic hyperglycemia.

Question 89: In urinalysis, a positive nitrite test indicates the presence of:

Urinary tract inflammation regardless of infection
High urinary protein concentration
Gram-negative bacteria that reduce nitrate to nitrite (Correct answer)
Gram-positive cocci such as Staphylococcus saprophyticus

Correct answer: Gram-negative bacteria that reduce nitrate to nitrite

The nitrite test detects bacteria (primarily Gram-negatives like E. coli) that convert dietary nitrate to nitrite via reductase enzymes; many Gram-positives lack this enzyme and produce a negative nitrite result.

Question 90: Which analyte requires a timed 24-hour urine collection for the most clinically meaningful result?

Creatinine clearance (Correct answer)
Urine pH
Urine glucose
Urine specific gravity

Correct answer: Creatinine clearance

Creatinine clearance requires a 24-hour urine collection to calculate glomerular filtration rate accurately by accounting for diurnal variation in excretion.

Question 91: An MLS suspects that a specimen was collected from a patient with an active IV line in the same arm without note on the requisition. Which result pattern would MOST support this concern?

Markedly decreased potassium and glucose with diluted electrolytes (Correct answer)
Elevated hemoglobin and hematocrit
Markedly decreased glucose with elevated sodium
Elevated creatinine with low eGFR

Correct answer: Markedly decreased potassium and glucose with diluted electrolytes

IV fluid contamination typically causes diluted electrolytes (low potassium, low sodium) and decreased glucose, reflecting the composition of the infusing fluid.

Question 92: Which skill is most important for success in Medical Terminology & Anatomy within Medical Laboratory Scientist?

Avoiding feedback
Continuous learning and adaptation (Correct answer)
Resisting change
Working without any training

Correct answer: Continuous learning and adaptation

Continuous learning ensures professionals stay current with evolving practices in Medical Terminology & Anatomy.

Question 93: A laboratory receives a specimen labeled only with a room number and no patient identifiers. The appropriate action is:

Accept with a verbal patient name from the nursing station
Reject the specimen and notify the clinical area to recollect (Correct answer)
Test the specimen and hold results pending identification
Process the specimen and add the identifier from the order

Correct answer: Reject the specimen and notify the clinical area to recollect

Two patient identifiers are required on every specimen; a label missing patient-specific identifiers renders the specimen unacceptable and it must be rejected to prevent patient identification errors.

Question 94: A gram-positive coccus in clusters is catalase-positive and coagulase-positive. Identification is:

Staphylococcus aureus (Correct answer)
Streptococcus pyogenes
Staphylococcus epidermidis
Enterococcus faecalis

Correct answer: Staphylococcus aureus

S. aureus is the only clinically significant Staphylococcus that is coagulase-positive; this distinguishes it from coagulase-negative staphylococci.

Question 95: Under CLSI and CAP guidelines, how often must laboratory emergency evacuation drills be conducted at minimum?

Every two years
Annually (Correct answer)
Monthly
Quarterly

Correct answer: Annually

Most accrediting bodies including CAP require at minimum annual fire/evacuation drills to ensure staff familiarity with emergency procedures.

Question 96: Which concept best describes the MLS's obligation to act in the patient's best interest above all other considerations?

Autonomy
Justice
Nonmaleficence
Beneficence (Correct answer)

Correct answer: Beneficence

Beneficence is the ethical principle requiring healthcare professionals to act in the best interest of the patient.

Question 97: Under Standard Precautions, which of the following body fluids requires the SAME level of precaution as blood?

Cerebrospinal fluid (Correct answer)
Sweat
Tears
Nasal secretions

Correct answer: Cerebrospinal fluid

Cerebrospinal fluid is listed under Standard Precautions as a body fluid posing infectious risk similar to blood.

Question 98: An MLS observes that a pediatric patient's wristband is loose and has slipped off onto the crib rail. What should happen before specimen collection?

Ask a parent or guardian to verbally confirm the child's name and date of birth
Replace or reattach the wristband with nursing staff verification before collection (Correct answer)
Collect the specimen and tape the wristband to the outside of the collection tube
Proceed with collection using the crib card as the sole identifier

Correct answer: Replace or reattach the wristband with nursing staff verification before collection

The wristband must be properly placed on the patient and verified with nursing staff before proceeding to maintain a reliable two-identifier check.

Question 99: A sputum Gram stain shows >25 squamous epithelial cells per low-power field. The laboratory should:

Process the specimen and report all organisms observed
Perform culture but note the poor quality in the report
Perform only acid-fast bacilli culture
Report the specimen as unsatisfactory and request a new sample (Correct answer)

Correct answer: Report the specimen as unsatisfactory and request a new sample

More than 25 squamous epithelial cells per LPF indicates heavy oral contamination, rendering the specimen unsatisfactory for lower respiratory tract culture; a repeat specimen should be requested.

Question 100: Which test is used to confirm a positive screening result for phenylketonuria (PKU) on a newborn dried blood spot?

Urine amino acid electrophoresis
Liver biopsy for phenylalanine hydroxylase activity
Plasma phenylalanine quantitation by tandem mass spectrometry (Correct answer)
Serum BH4 loading test alone

Correct answer: Plasma phenylalanine quantitation by tandem mass spectrometry

Confirmatory testing for PKU uses quantitative plasma phenylalanine measurement (typically by LC-MS/MS), which precisely determines phenylalanine levels to guide diagnosis and management.

Medical Laboratory Scientist (MLS) Examination — ASCP Board of Certification

The MLS(ASCP) certification exam validates competency across all major clinical laboratory disciplines including blood banking, chemistry, hematology, microbiology, immunology, urinalysis, and laboratory operations. It is administered as a 100-question Computer Adaptive Test (CAT) by the ASCP Board of Certification.

100

Questions

150 min

Time Limit

70%

To Pass

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