A wrong tube, a stale sample or an unbalanced centrifuge can produce a result that looks real and is not. The exam rewards knowing why each handling step exists, not just the step itself.
3 sample Laboratory Procedures questions
Try each one before opening the answer. These come straight from the VetTech Pro question bank.
Question 1. Which anticoagulant is the standard choice for a complete blood count?
AEDTA (lavender top)
BSodium citrate (blue top)
CSodium fluoride (gray top)
DLithium heparin (green top)
Show answer and rationale
Answer: A. EDTA (lavender top)
EDTA preserves cell morphology better than any other routine anticoagulant, which is what a CBC depends on. Heparin causes leukocyte clumping and a blue tinge on Romanowsky stains; citrate is for coagulation testing; fluoride is a glycolysis inhibitor for glucose.
Question 2. Why must a patient be fed a meat-free diet before a fecal occult blood test?
AThe test is valid only when the patient has been fasted
BMeat raises fecal pH and inactivates the guaiac reagent
CDietary hemoglobin and myoglobin cause false-positive reactions
DMeat proteins coat the guaiac test card and inhibit the color reaction
Show answer and rationale
Answer: C. Dietary hemoglobin and myoglobin cause false-positive reactions
Guaiac-based tests detect peroxidase activity, which dietary hem provides, so meat produces a positive independent of any bleeding. Three days on a meat-free diet is typically required for the result to mean anything.
Question 3. Why might an automated analyzer report a falsely low platelet count in a cat sample?
AFeline plasma proteins interfere with the counting chamber
BMost analyzers lack a validated feline setting for counting platelets
CFeline platelets clump, and clumps are excluded from the count
DFeline platelets lyse in EDTA within minutes of collection
Show answer and rationale
Answer: C. Feline platelets clump, and clumps are excluded from the count
Platelet clumping is common in cats and causes the analyzer to undercount, since clumped platelets are not counted as individual cells. A blood smear estimate is used to confirm or refute a low automated count before acting on it.
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