MLS Clinical Testing & Analysis 2 — Questions and Answers
Question 1: A patient's serum glucose is 54 mg/dL on a fasting specimen. Which confirmatory step is most appropriate?
- Repeat testing on a new fasting specimen (Correct answer)
- Perform a glucose tolerance test immediately
- Report the result without further action
- Order a urine glucose dipstick
Correct answer: Repeat testing on a new fasting specimen
A fasting glucose of 54 mg/dL is hypoglycemic and should be confirmed with repeat testing on a fresh specimen to rule out pre-analytical errors.
Question 2: Which reagent in the Wright-Giemsa stain is responsible for staining acidic cellular components pink/red?
- Eosin Y (Correct answer)
- Azure B
- Methylene blue
- Crystal violet
Correct answer: Eosin Y
Eosin Y is the acidic dye in Wright-Giemsa that binds to basic (positively charged) cellular components such as hemoglobin and eosinophil granules, staining them pink to red.
Question 3: A PT result is markedly prolonged but the PTT is normal. Which factor deficiency is most consistent with this pattern?
- Factor VII (Correct answer)
- Factor VIII
- Factor XII
- Factor IX
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 4: A urine specific gravity of 1.001 most likely indicates:
- Diabetes insipidus or overhydration (Correct answer)
- Dehydration
- Urinary tract infection
- Nephrotic syndrome
Correct answer: Diabetes insipidus or overhydration
Specific gravity of 1.001 represents maximally dilute urine, consistent with diabetes insipidus or excessive fluid intake.
Question 5: In the Kirby-Bauer disk diffusion method, which standard is used to prepare the bacterial inoculum?
- 0.5 McFarland standard (Correct answer)
- 1.0 McFarland standard
- 2.0 McFarland standard
- ATCC turbidity standard
Correct answer: 0.5 McFarland standard
CLSI guidelines specify a 0.5 McFarland turbidity standard (~1–2 × 10⁸ CFU/mL) for inoculum preparation in Kirby-Bauer testing.
Question 6: Which lipoprotein is primarily responsible for transporting dietary triglycerides from the intestine to peripheral tissues?
- Chylomicrons (Correct answer)
- VLDL
- LDL
- HDL
Correct answer: Chylomicrons
Chylomicrons are synthesized in intestinal epithelial cells and carry dietary (exogenous) triglycerides through lymph to peripheral tissues.
Question 7: A hemoglobin electrophoresis at alkaline pH shows a band migrating to the same position as HbS. Which additional test best distinguishes HbS from HbD?
- Acid pH electrophoresis (Correct answer)
- Solubility (sickle) test
- HPLC alone
- Osmotic fragility test
Correct answer: Acid pH electrophoresis
HbS and HbD co-migrate at alkaline pH but separate on acid (citrate agar) electrophoresis: HbS migrates toward the cathode while HbD remains near the origin.
MLS Clinical Testing & Analysis 2
A patient's serum glucose is 54 mg/dL on a fasting specimen.
Which confirmatory step is most appropriate?