CVA Laboratory Techniques and Diagnostic Procedures 4 — Questions and Answers
Question 1: When performing a blood smear using the push-slide technique, what does a smear that is too thick most likely indicate?
- The spreader slide angle was too low (less than 30°)
- The spreader slide was pushed too slowly
- The spreader slide angle was too high (greater than 45°) or a large drop of blood was used (Correct answer)
- The blood sample was too old
Correct answer: The spreader slide angle was too high (greater than 45°) or a large drop of blood was used
A steep angle or too large a blood drop produces a thick smear where cells overlap, making differential counting unreliable.
Question 2: Heinz bodies visible on a feline blood smear are caused by what?
- Iron deficiency leading to microcytic RBCs
- Oxidative damage to hemoglobin forming denatured protein inclusions (Correct answer)
- Immune-mediated destruction of red blood cells
- Reticulocyte maturation artifacts
Correct answer: Oxidative damage to hemoglobin forming denatured protein inclusions
Heinz bodies are precipitates of oxidatively denatured hemoglobin attached to the RBC membrane, commonly caused by onions, acetaminophen, or propylene glycol in cats.
Question 3: A urine sediment examined microscopically reveals waxy casts. What does this finding suggest about the duration of renal tubular disease?
- Acute, short-term tubular injury
- Very recent glomerular damage
- Chronic, long-standing tubular disease (Correct answer)
- Normal finding in healthy animals
Correct answer: Chronic, long-standing tubular disease
Waxy casts form from the degeneration of granular casts over time, indicating chronic, severe renal tubular disease with prolonged urinary stasis.
Question 4: Which staining method is used specifically to identify reticulocytes (immature red blood cells) in a blood sample?
- Wright-Giemsa stain
- Gram stain
- New methylene blue (NMB) stain (Correct answer)
- Acid-fast stain
Correct answer: New methylene blue (NMB) stain
New methylene blue is a supravital stain that precipitates residual RNA in reticulocytes, making them appear as cells with dark blue granules or a network.
Question 5: What is the primary purpose of using a Baermann apparatus in veterinary diagnostics?
- Concentrating parasite eggs by flotation
- Recovering motile larvae (especially lungworm larvae) from fecal samples (Correct answer)
- Separating serum from clotted blood
- Detecting Giardia cysts using zinc sulfate solution
Correct answer: Recovering motile larvae (especially lungworm larvae) from fecal samples
The Baermann technique uses the larvaes' motility and warmth-seeking behavior to migrate out of feces into water, concentrating them at the bottom for identification.
Question 6: In a urinalysis, a urine pH of 8.5 in a dog that has been fasted overnight is most suspicious for which condition?
- Diabetes mellitus
- Urinary tract infection with urease-producing bacteria (Correct answer)
- Ethylene glycol toxicity
- Hepatic lipidosis
Correct answer: Urinary tract infection with urease-producing bacteria
Urease-producing bacteria (e.g., Staphylococcus, Proteus) split urea into ammonia, dramatically raising urine pH toward alkaline levels.
Question 7: Which plasma color indicates lipemia in a centrifuged blood sample?
- Yellow (icteric)
- Clear and pale yellow
- Milky white or turbid (Correct answer)
- Pink to red (hemolyzed)
Correct answer: Milky white or turbid
Lipemia causes plasma to appear milky white or turbid due to chylomicrons and very low-density lipoproteins scattering light.
CVA Laboratory Techniques and Diagnostic Procedures 4
When performing a blood smear using the push-slide technique, what does a smear that is too thick most likely indicate?