CVA Laboratory Techniques and Diagnostic Procedures 5 — Questions and Answers
Question 1: When preparing a bacterial culture swab from a wound, which transport medium is most appropriate to maintain organism viability during shipping?
- Nutrient broth at 37°C
- Amies or Stuart transport medium (Correct answer)
- MacConkey agar plate
- Thioglycolate broth in a sealed syringe
Correct answer: Amies or Stuart transport medium
Amies and Stuart transport media maintain moisture and preserve bacterial viability without allowing significant growth or drying during transit to the lab.
Question 2: A BUN (blood urea nitrogen) to creatinine ratio greater than 20:1 in a dehydrated dog most likely indicates what type of azotemia?
- Intrinsic renal (renal) azotemia
- Post-renal azotemia from urethral obstruction
- Pre-renal azotemia due to reduced renal perfusion (Correct answer)
- Hepatic azotemia from liver failure
Correct answer: Pre-renal azotemia due to reduced renal perfusion
Pre-renal azotemia causes disproportionate BUN elevation relative to creatinine because the kidney reabsorbs urea more avidly when perfusion is low, raising the BUN:Cr ratio above 20:1.
Question 3: Which type of microscope objective is used to identify microfilariae in a modified Knott's test preparation?
- Oil immersion (100×)
- High dry (40×)
- Low power (10×) (Correct answer)
- Scanning (4×)
Correct answer: Low power (10×)
The 10× objective (low power) is used first to scan for microfilariae because they are large enough to be visible at low magnification and are easier to find across the field.
Question 4: What does the term 'isosthenuria' mean in the context of a urinalysis?
- Urine specific gravity equal to that of glomerular filtrate (1.008–1.012), indicating tubular inability to concentrate or dilute (Correct answer)
- Urine with abnormally high protein content
- Urine that contains glucose and ketones simultaneously
- Complete absence of urine production
Correct answer: Urine specific gravity equal to that of glomerular filtrate (1.008–1.012), indicating tubular inability to concentrate or dilute
Isosthenuria (USG 1.008–1.012) means the kidney can neither concentrate nor dilute urine beyond plasma ultrafiltrate, signaling severe tubular dysfunction.
Question 5: A Diff-Quik stained impression smear from a skin lesion reveals numerous round organisms with a clear halo inside macrophages. What is the most likely organism?
- Sporothrix schenckii
- Cryptococcus neoformans (Correct answer)
- Histoplasma capsulatum
- Malassezia pachydermatis
Correct answer: Cryptococcus neoformans
Cryptococcus neoformans appears as round yeast with a prominent clear polysaccharide capsule (halo) and is commonly found inside macrophages on cytology.
Question 6: Which laboratory finding is most consistent with a regenerative anemia in a dog?
- MCV within normal range, no polychromasia
- Increased polychromasia and elevated reticulocyte count (Correct answer)
- Decreased MCH with normal reticulocyte count
- Hypersegmented neutrophils on differential
Correct answer: Increased polychromasia and elevated reticulocyte count
Regenerative anemia is characterized by increased reticulocytes (immature RBCs) and polychromasia (blue-tinged cells on Wright stain) as the bone marrow responds to RBC loss.
Question 7: When collecting a urine sample by cystocentesis, what is the primary advantage over a free-catch sample for culture and sensitivity testing?
- Larger sample volume is obtained
- The sample is collected without contamination from the urethra, prepuce, or vulva (Correct answer)
- Cystocentesis samples have a higher specific gravity
- The procedure is less stressful for the patient
Correct answer: The sample is collected without contamination from the urethra, prepuce, or vulva
Cystocentesis bypasses the lower urogenital tract, eliminating environmental and commensal bacterial contamination and providing a sterile bladder sample ideal for culture.
CVA Laboratory Techniques and Diagnostic Procedures 5
When preparing a bacterial culture swab from a wound, which transport medium is most appropriate to maintain organism viability during shipping?