TEXAS CLINICAL LABORATORY SCIENTIST
LICENSE EXAM PRACTICE QUESTIONS
AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
| INSTANT DOWNLOAD PDF
1. Which anticoagulant is preferred for routine hematology
(CBC) testing?
A. Heparin
B. EDTA
C. Citrate
D. Oxalate
Rationale: EDTA chelates calcium and preserves cellular
morphology for CBC and differential counts.
2. A serum sample is needed for chemistry testing but the
specimen submitted is collected in a lavender-top tube.
What is the appropriate action?
A. Proceed with testing after centrifugation
B. Request a new specimen collected in a clot tube (red or
SST).
C. Use plasma instead for all tests
, D. Add thrombin to clot the sample
Rationale: Serum-required assays need clotting; EDTA-
plasma is inappropriate and will give inaccurate results.
3. Which wavelength range is most commonly used for
measuring NADH/NADPH absorbance in enzymatic assays?
A. 200–220 nm
B. 260–280 nm
C. 340 nm
D. 600 nm
Rationale: NADH and NADPH absorb at 340 nm,
commonly used to follow enzymatic reactions.
4. The most likely cause of persistently low control values
when patient results are acceptable is:
A. Random error in patient samples
B. Systematic error in the control material or calibration
drift.
C. Hemolysis in patient samples
D. Increased assay sensitivity
Rationale: Low control values with acceptable patient
data suggest control or calibration issues (systematic).
5. In microbiology, mannitol salt agar is selective and
differential for:
A. Gram-negative rods
B. Staphylococcus species (distinguishes S. aureus by
, mannitol fermentation).
C. Enterococci
D. Streptococci
Rationale: High salt selects staphylococci; mannitol
fermentation differentiates S. aureus (yellow colonies).
6. What is the best indicator of acute myocardial infarction
when measured serially in the first 24 hours?
A. Myoglobin only
B. Total CK only
C. Cardiac troponin I or T (serially elevated).
D. LDH isoenzymes only
Rationale: Cardiac troponins are highly specific and
remain elevated for days, useful for diagnosis.
7. A bilirubin specimen for neonatal testing should be:
A. Collected in a lavender-top tube
B. Stored at 37°C
C. Protected from light and processed promptly.
D. Frozen before analysis
Rationale: Bilirubin is light-sensitive; protect from light to
prevent degradation.
8. Which instrument principle is used in flow cytometry to
measure cell size?
A. Fluorescence polarization
B. Forward scatter (light scatter).
, C. Nephelometry
D. Turbidimetry
Rationale: Forward scatter correlates with cell size in flow
cytometry.
9. A Gram-positive bacillus that forms endospores and shows
square ends likely belongs to:
A. Corynebacterium (club-shaped)
B. Bacillus species (endospore-forming rods).
C. Listeria monocytogenes
D. Clostridium difficile
Rationale: Bacillus are gram-positive rods with
endospores and typical square ends.
10. The anion gap is calculated as (Na⁺ + K⁺) - (Cl⁻ +
HCO₃⁻). A high anion gap suggests:
A. Hypochloremia only
B. Presence of unmeasured anions (e.g., lactic acidosis,
ketoacidosis).
C. Hypernatremia only
D. Metabolic alkalosis
Rationale: Elevated anion gap indicates accumulation of
unmeasured anions leading to metabolic acidosis.
11. Which blood bank test determines ABO grouping?
A. Indirect antiglobulin test
B. Forward and reverse grouping (cell and serum typing).
LICENSE EXAM PRACTICE QUESTIONS
AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
| INSTANT DOWNLOAD PDF
1. Which anticoagulant is preferred for routine hematology
(CBC) testing?
A. Heparin
B. EDTA
C. Citrate
D. Oxalate
Rationale: EDTA chelates calcium and preserves cellular
morphology for CBC and differential counts.
2. A serum sample is needed for chemistry testing but the
specimen submitted is collected in a lavender-top tube.
What is the appropriate action?
A. Proceed with testing after centrifugation
B. Request a new specimen collected in a clot tube (red or
SST).
C. Use plasma instead for all tests
, D. Add thrombin to clot the sample
Rationale: Serum-required assays need clotting; EDTA-
plasma is inappropriate and will give inaccurate results.
3. Which wavelength range is most commonly used for
measuring NADH/NADPH absorbance in enzymatic assays?
A. 200–220 nm
B. 260–280 nm
C. 340 nm
D. 600 nm
Rationale: NADH and NADPH absorb at 340 nm,
commonly used to follow enzymatic reactions.
4. The most likely cause of persistently low control values
when patient results are acceptable is:
A. Random error in patient samples
B. Systematic error in the control material or calibration
drift.
C. Hemolysis in patient samples
D. Increased assay sensitivity
Rationale: Low control values with acceptable patient
data suggest control or calibration issues (systematic).
5. In microbiology, mannitol salt agar is selective and
differential for:
A. Gram-negative rods
B. Staphylococcus species (distinguishes S. aureus by
, mannitol fermentation).
C. Enterococci
D. Streptococci
Rationale: High salt selects staphylococci; mannitol
fermentation differentiates S. aureus (yellow colonies).
6. What is the best indicator of acute myocardial infarction
when measured serially in the first 24 hours?
A. Myoglobin only
B. Total CK only
C. Cardiac troponin I or T (serially elevated).
D. LDH isoenzymes only
Rationale: Cardiac troponins are highly specific and
remain elevated for days, useful for diagnosis.
7. A bilirubin specimen for neonatal testing should be:
A. Collected in a lavender-top tube
B. Stored at 37°C
C. Protected from light and processed promptly.
D. Frozen before analysis
Rationale: Bilirubin is light-sensitive; protect from light to
prevent degradation.
8. Which instrument principle is used in flow cytometry to
measure cell size?
A. Fluorescence polarization
B. Forward scatter (light scatter).
, C. Nephelometry
D. Turbidimetry
Rationale: Forward scatter correlates with cell size in flow
cytometry.
9. A Gram-positive bacillus that forms endospores and shows
square ends likely belongs to:
A. Corynebacterium (club-shaped)
B. Bacillus species (endospore-forming rods).
C. Listeria monocytogenes
D. Clostridium difficile
Rationale: Bacillus are gram-positive rods with
endospores and typical square ends.
10. The anion gap is calculated as (Na⁺ + K⁺) - (Cl⁻ +
HCO₃⁻). A high anion gap suggests:
A. Hypochloremia only
B. Presence of unmeasured anions (e.g., lactic acidosis,
ketoacidosis).
C. Hypernatremia only
D. Metabolic alkalosis
Rationale: Elevated anion gap indicates accumulation of
unmeasured anions leading to metabolic acidosis.
11. Which blood bank test determines ABO grouping?
A. Indirect antiglobulin test
B. Forward and reverse grouping (cell and serum typing).
