CVA Laboratory Sample Handling 4 — Questions and Answers
Question 1: When collecting a urine sample for culture and sensitivity, which collection method is preferred to avoid contamination?
- Free catch midstream
- Cystocentesis (Correct answer)
- Catheterization
- Manual bladder expression
Correct answer: Cystocentesis
Cystocentesis (needle aspiration directly from the bladder) provides the most sterile urine sample for bacterial culture, avoiding urethral and environmental contamination.
Question 2: A fecal flotation test is used to detect which type of parasites?
- Tapeworm proglottids
- Eggs and oocysts of intestinal parasites (Correct answer)
- Adult heartworms
- Larval stages of Toxocara
Correct answer: Eggs and oocysts of intestinal parasites
Fecal flotation uses a high-density solution to float parasite eggs and oocysts to the surface for microscopic identification.
Question 3: Which anticoagulant tube is used when collecting blood for a complete blood count (CBC)?
- Red top (no additive)
- Green top (heparin)
- Purple/lavender top (EDTA) (Correct answer)
- Blue top (sodium citrate)
Correct answer: Purple/lavender top (EDTA)
EDTA (purple/lavender top) is the anticoagulant of choice for CBC because it best preserves cell morphology and prevents clotting without affecting cell counts.
Question 4: How should a blood smear be stored if it cannot be stained immediately?
- In a sealed container with saline
- Air-dried and protected from dust and moisture (Correct answer)
- Refrigerated in a tube of EDTA blood
- Wrapped in wet gauze to prevent drying
Correct answer: Air-dried and protected from dust and moisture
Blood smears should be air-dried quickly and stored in a clean, dry slide box to preserve cell morphology until staining.
Question 5: What is the correct temperature for storing most urine samples awaiting analysis?
- Room temperature (20–25°C)
- Frozen at -20°C
- Refrigerated at 2–8°C (Correct answer)
- Incubated at 37°C
Correct answer: Refrigerated at 2–8°C
Urine samples should be refrigerated at 2–8°C to slow bacterial growth and cellular deterioration, ideally analyzed within 30–60 minutes of collection.
Question 6: Which stain is most commonly used to perform a differential white blood cell count on a blood smear?
- Gram stain
- Wright-Giemsa stain (Correct answer)
- India ink
- Methylene blue only
Correct answer: Wright-Giemsa stain
Wright-Giemsa stain differentiates white blood cell types by staining nuclear and cytoplasmic components different colors, enabling differential counts.
Question 7: When is it necessary to use a gray-top (sodium fluoride/potassium oxalate) tube for blood collection?
- For coagulation testing
- For serum chemistry panels
- For blood glucose measurement requiring delayed analysis (Correct answer)
- For complete blood counts
Correct answer: For blood glucose measurement requiring delayed analysis
Gray-top tubes contain sodium fluoride, which inhibits glycolysis, preserving glucose levels in samples that cannot be analyzed immediately.
CVA Laboratory Sample Handling 4
When collecting a urine sample for culture and sensitivity, which collection method is preferred to avoid contamination?