Laboratory Procedures

9% of the VTNE · blueprint VTNE content outline approved by the AAVSB Board, March 2023

Short answer

Laboratory Procedures is 14 of the 150 scored VTNE items. It covers sample collection, handling and preparation including tube selection and order of draw; haematology, clinical chemistry, urinalysis, cytology and parasitology; quality control and instrument maintenance; and recognising results that require the veterinarian's immediate attention.

Why it matters on this exam

Pre-analytical error — the wrong tube, a delayed sample, a haemolysed draw — is the most common source of a wrong result, and the exam tests it.

Key concepts

Tubes and additives: EDTA for haematology, heparin and serum tubes for chemistry, citrate for coagulation with the correct fill ratio, fluoride oxalate for glucose preservation.
Sample handling: separate serum promptly, avoid haemolysis and lipaemia, refrigerate urine if analysis is delayed and note the effect on crystals.
Haematology: PCV and total solids interpretation together, blood-film review for platelet clumps before reporting thrombocytopenia, and the species differences in white-cell responses.
Urinalysis: specific gravity interpreted against hydration and species, sediment findings, and the effect of standing time.
Parasitology: faecal flotation versus direct smear versus sedimentation, and which parasites each detects.
Quality control: running controls, recording results, and recognising drift before patient samples are reported.

Common mistakes

Reporting a low automated platelet count without checking the smear for clumping.
Using an underfilled citrate tube, which alters coagulation times.

Worked example

An analyser reports severe thrombocytopenia in a cat with no bleeding signs. Cat platelets clump readily, so a blood-film estimate is required before the result is reported.

Original practice questions

Laboratory ProceduresDifficulty 3/5

An automated analyser reports severe thrombocytopenia in a cat with no bleeding signs. What should be done before the result is reported?

ARepeat the sample in a citrate tube to confirm the platelet count
BExamine a blood film to estimate platelets and check for clumping
CReport the result immediately, since analysers are more precise
DRecollect from a different vein using a larger-gauge needle

Show answer and rationale

Correct: B. Feline platelets clump readily, which causes falsely low automated counts. A film estimate confirms or refutes the count before any result is reported.

A — Citrate is for coagulation testing and does not resolve the question.
C — Analysers systematically undercount clumped feline platelets.
D — Recollection may be needed later but the film check comes first.

Laboratory ProceduresDifficulty 2/5

Which tube is appropriate for a complete blood count?

AA sodium citrate tube, which is filled to the marked ratio line
BA lithium heparin tube, which prevents clotting without cell damage
CAn EDTA tube, which preserves cell morphology for haematology
DA plain serum tube, which allows the sample to clot before analysis

Show answer and rationale

Correct: C. EDTA is the anticoagulant of choice for haematology because it preserves cell morphology. Heparin distorts staining, serum tubes clot, and citrate is for coagulation testing.

B — Heparin interferes with Romanowsky staining of blood films.
D — A clotted sample cannot give a cell count.
A — Citrate dilution is designed for coagulation assays.

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2 flashcards for Laboratory Procedures

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Blueprint-mapped questions with full rationales for every choice.

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Primary references

VTNE Candidate Information Handbook — American Association of Veterinary State Boards (AAVSB) · primary · retrieved 2026-09-22, verified 2026-09-22

Last reviewed: 2026-09-22Next review by: 2026-11-06Draft — pending editorial reviewHow we verify facts