CVA Laboratory Techniques & Diagnostic Procedures 3 — Questions and Answers
Question 1: What is the correct needle angle for venipuncture of the cephalic vein in a dog?
- 15–30 degrees (Correct answer)
- 90 degrees
- 45–60 degrees
- 5 degrees
Correct answer: 15–30 degrees
A 15–30 degree angle allows the needle to enter the vein smoothly without passing through the opposite wall.
Question 2: Which finding on a urinalysis sediment examination is most indicative of a bacterial urinary tract infection?
- Bacteria and white blood cells (pyuria) (Correct answer)
- Struvite crystals only
- Transitional epithelial cells
- Red blood cell casts
Correct answer: Bacteria and white blood cells (pyuria)
The combination of bacteria and white blood cells (pyuria) in urine sediment strongly suggests active bacterial infection.
Question 3: A packed cell volume (PCV) of 18% in a cat most likely indicates:
- Anemia (Correct answer)
- Polycythemia
- Normal hematocrit
- Dehydration
Correct answer: Anemia
Normal PCV in cats is 24–45%; a PCV of 18% is below the reference range, indicating anemia.
Question 4: When reading a fecal flotation slide under the microscope, which objective lens is typically used first?
- 4x or 10x (low power) (Correct answer)
- 40x (high-dry)
- 100x oil immersion
- 60x
Correct answer: 4x or 10x (low power)
Low-power objectives (4x or 10x) are used first to scan the entire coverslip area before switching to higher magnification for identification.
Question 5: What is the purpose of adding EDTA anticoagulant to a blood collection tube?
- It chelates calcium to prevent clotting (Correct answer)
- It kills bacteria in the sample
- It lyses red blood cells for easier counting
- It preserves serum proteins
Correct answer: It chelates calcium to prevent clotting
EDTA chelates (binds) calcium ions, which are required for the clotting cascade, thus preventing coagulation.
Question 6: Which diagnostic test is most appropriate for identifying ringworm (dermatophytosis) in a cat?
- Fungal culture (DTM agar) and Wood's lamp examination (Correct answer)
- Fecal flotation
- Complete blood count
- Urine sediment exam
Correct answer: Fungal culture (DTM agar) and Wood's lamp examination
Dermatophyte Test Medium (DTM) fungal culture is the gold standard for diagnosing ringworm, and a Wood's lamp can screen for Microsporum canis fluorescence.
Question 7: In a blood smear, platelets are best evaluated using which objective?
- 100x oil immersion (Correct answer)
- 4x
- 10x
- 20x
Correct answer: 100x oil immersion
Platelets are very small and must be viewed under 100x oil immersion to accurately assess their morphology and estimate numbers.
CVA Laboratory Techniques & Diagnostic Procedures 3
What is the correct needle angle for venipuncture of the cephalic vein in a dog?