VTNE Laboratory Review: Hematology, Urinalysis & Parasitology

Laboratory procedures are one of the most tangible, technique-heavy sections of the Veterinary Technician National Exam. Instead of pure memorization, this domain tests whether you can run and interpret the bench work that drives diagnosis: a CBC and blood smear, a clinical chemistry panel, a complete urinalysis with sediment, a fecal flotation, and a cytology prep — plus the sample handling, tube selection, and quality control that keep those results trustworthy. This VTNE laboratory review walks through the high-yield facts in each area and gives you worked exam-style questions with full rationales.

Last verified: June 2026 against the Merck Veterinary Manual, Cornell and eClinPath clinical-pathology references, and the AAVSB VTNE Candidate Handbook. Always confirm current exam structure and fees on aavsb.org.

What laboratory topics are on the VTNE?

The official VTNE is built on 9 domains, and "Laboratory Procedures" is one of them. It covers hematology, clinical chemistry, urinalysis, parasitology, cytology, microbiology basics, sample collection and handling, and quality control. On vtneexam.com, your practice is organized into 12 study categories — those official 9 domains plus three the platform breaks out separately (Communication & Ethics, Exotic Animal, Large Animal) — so the Laboratory material has its own filtered question set and flashcard deck.

For the full blueprint and how each section is weighted, see our VTNE domains breakdown. Because lab values drive clinical decisions, pair this page with the sibling reviews for VTNE pharmacology and VTNE diagnostic imaging.

Key concepts and high-yield laboratory topics

Hematology and blood smear evaluation

Hematology starts with the complete blood count (CBC). A quick, high-yield bench test you must know cold is the PCV/TP: spin a microhematocrit capillary tube and read two numbers. The packed cell volume (PCV) is the percent of the column that is red cells, measured after centrifugation; the total protein (TP, or total solids) is read from the plasma using a refractometer. Between the packed red cells and the plasma sits the buffy coat, a thin grayish-white band of white blood cells and platelets — a markedly thick buffy coat suggests leukocytosis.

The blood film lets you do a WBC differential (counting neutrophils, lymphocytes, monocytes, eosinophils, and basophils), estimate platelet numbers, and assess red-cell morphology. Read the smear in the monolayer, just behind the feathered edge, where cells lie in a single layer. A few testable rules:

• The preferred anticoagulant for a CBC and blood smear is EDTA (lavender/purple top) because it preserves cell morphology.
• Always make smears from fresh, well-mixed EDTA blood as soon as possible; prolonged storage causes artifact.
• Common red-cell findings include polychromasia and reticulocytes (signs of a regenerative, responding anemia), spherocytes (immune-mediated hemolysis), and Heinz bodies (oxidative damage, classically in cats).

Clinical chemistry, cytology, and quality control

Clinical chemistry measures organ and metabolic analytes from serum (red-top, no anticoagulant — let it clot fully, then spin) or heparinized plasma. High-yield groupings the VTNE tests: ALT, AST, ALP, GGT, and bilirubin for the liver; BUN and creatinine for the kidney; glucose; total protein and albumin; and electrolytes (Na, K, Cl). Hemolysis and lipemia are classic interferents that can falsely shift several analytes, so technique matters.

Cytology is the microscopic study of cells from fluids, fine-needle aspirates, or impression smears. The skills tested are sample collection, slide preparation (the "squash" or blood-smear pull), staining with a Romanowsky-type stain such as Diff-Quik, and basic recognition of inflammation versus neoplasia. Cytology and microbiology samples for culture must be collected aseptically and handled to avoid contamination.

Quality control ties the whole domain together: run controls on analyzers, calibrate and clean equipment (refractometers, centrifuges, microscopes), label every sample correctly, log results, and select the correct tube for each test. The exam frequently checks whether you can match an analyte to the right tube and anticoagulant.

Urinalysis and crystal/bladder-stone identification

A complete urinalysis has three parts: physical (color, clarity, and specific gravity by refractometer), chemical (dipstick for pH, protein, glucose, ketones, blood, bilirubin), and microscopic sediment exam. Urine specific gravity (USG) reflects how well the kidneys concentrate urine and is read on a refractometer; you must interpret it together with hydration status. Sediment can reveal red and white blood cells, casts, bacteria, epithelial cells, and crystals.

Crystals are a favorite VTNE topic, and they tie directly into how bladder-stone (urolith) types are presumptively identified. The key link is urine pH:

• Struvite (magnesium ammonium phosphate) crystals form in alkaline urine and appear as colorless "coffin-lid" prisms. They are the most common crystal in dogs and cats and are often associated with urinary tract infection by urease-producing bacteria.
• Calcium oxalate crystals form in acidic-to-neutral urine; the dihydrate form looks like a small colorless square with an X inside (an "envelope").
• Ammonium biurate crystals ("thorn-apple" spheres) suggest liver dysfunction or a portosystemic shunt.
• Cystine crystals are flat colorless hexagons and indicate an inherited tubular transport defect.

So bladder-stone type is identified by combining the urine pH, the crystal morphology under the microscope, imaging (radiographs/ultrasound), signalment, and — definitively — laboratory analysis of a retrieved stone. A presumptive call of struvite, for example, rests on alkaline urine plus numerous coffin-lid crystals plus often a positive urine culture.

Parasitology: fecal floats, ova, and vectors

The most common in-clinic parasitology test is the fecal flotation. It works because most helminth eggs and protozoal oocysts have a specific gravity lower than the flotation solution, so they rise to the surface and adhere to a coverslip. Common solutions include sodium nitrate, saturated sodium chloride, and sugar (Sheather's); zinc sulfate is preferred when you suspect Giardia, because the high-density salt solutions distort its fragile cysts. Centrifugal flotation recovers more eggs than simple (passive) flotation.

Know the vector-borne side too: heartworm (Dirofilaria immitis) is transmitted by mosquitoes and diagnosed by an antigen test, not a fecal float; ticks transmit Borrelia (Lyme), Ehrlichia, and Anaplasma; and a direct saline smear of fresh feces is the method to catch motile protozoal trophozoites.

Worked example VTNE-style questions

Question 1. Which blood collection tube is the correct choice for a complete blood count and blood smear? A) Red top   B) Lavender top (EDTA)   C) Blue top (citrate)   D) Green top (heparin)

Answer: B) Lavender top (EDTA). EDTA is the anticoagulant of choice for hematology because it best preserves cell morphology. Citrate (blue) is for coagulation testing, heparin (green) causes cell clumping that invalidates counts, and a red top yields serum for chemistry, not whole blood for a CBC.

Question 2. A canine urinalysis shows alkaline urine (pH 8.0) with numerous colorless, coffin-lid-shaped crystals and a positive culture. Which urolith type is most consistent with these findings? A) Calcium oxalate   B) Cystine   C) Struvite   D) Ammonium biurate

Answer: C) Struvite. Struvite (magnesium ammonium phosphate) forms in alkaline urine, has classic coffin-lid prism crystals, and is frequently linked to infection with urease-producing bacteria. Calcium oxalate forms in acidic urine, cystine appears as hexagons, and ammonium biurate suggests liver/portosystemic-shunt disease.

Question 3. A technician suspects Giardia. Which flotation solution should be used to best preserve the organism's cysts? A) Saturated sodium chloride   B) Sugar (Sheather's)   C) Zinc sulfate   D) Sodium nitrate

Answer: C) Zinc sulfate. The high-density salt and sugar solutions tend to distort and collapse the fragile Giardia cysts, making them hard to recognize; zinc sulfate is the preferred medium for Giardia recovery.

Want hundreds more in this format? Try a set of VTNE practice questions or take a full-length free VTNE practice test.

Common mistakes and how laboratory is tested

• Wrong tube for the test. Submitting EDTA blood for a chemistry panel, or serum for a CBC, is a classic trap. Match analyte to tube every time.
• Reading the smear in the wrong zone. Differentials and morphology are assessed in the monolayer behind the feathered edge, not the thick body of the film.
• Ignoring urine pH with crystals. Crystal identity hinges on pH — struvite (alkaline) versus calcium oxalate (acidic). Read them together.
• Treating crystals as a diagnosis. Crystalluria supports but does not confirm a stone; definitive urolith identity comes from laboratory stone analysis.
• Using the wrong float solution for Giardia. Standard salt/sugar floats distort the cysts; zinc sulfate is the answer.
• Skipping quality control. Uncalibrated refractometers, dirty optics, and mislabeled samples generate wrong results that the exam expects you to catch.

How to study the Laboratory domain

This domain rewards pattern recognition: you need to instantly link a finding (alkaline pH, coffin-lid crystals) to a conclusion (likely struvite), or a test (CBC) to its tube (EDTA). Build a daily flashcard habit for tube colors, crystal shapes, parasite ova, and normal value ranges, then drill domain-filtered questions under timed conditions so the connections become reflexive. A free Quizlet deck can get you started, but it is unverified user content — vtneexam.com gives you a curated 2,283-card flashcard deck and a timed 2,757-question practice bank, every question written with a full answer rationale and filtered by domain so you can target Laboratory Procedures specifically.

Practice Laboratory questions free and start a timed VTNE exam to see exactly how ready you are.

Frequently Asked Questions

How are bladder stone types identified?

Bladder-stone (urolith) type is identified by combining several clues: urine pH and crystal morphology on sediment exam (struvite forms coffin-lid crystals in alkaline urine; calcium oxalate forms envelope-shaped crystals in acidic urine), imaging with radiographs or ultrasound, the patient's signalment, and urine culture. The definitive method, however, is laboratory analysis of a stone that has been retrieved surgically, by voiding, or by lithotripsy.

What parasitology topics show up on the VTNE?

Expect fecal flotation technique and solutions (sodium nitrate, sugar, and zinc sulfate for Giardia), recognition of common ova — roundworm (Toxocara), hookworm (Ancylostoma), whipworm (Trichuris), tapeworm, and coccidia — plus protozoa such as Giardia, the direct fecal smear for motile trophozoites, and vector-borne disease basics like mosquito-transmitted heartworm and tick-borne Lyme, Ehrlichia, and Anaplasma.

What is the difference between EDTA, heparin, and citrate tubes?

EDTA (lavender top) chelates calcium and best preserves cell morphology, so it is used for the CBC and blood smear. Sodium citrate (blue top) reversibly binds calcium and is used for coagulation tests such as PT and aPTT. Heparin (green top) yields plasma for chemistry and blood-gas analysis but is not used for cell counts because it causes cells to clump.

How do you read a PCV and total protein?

Spin EDTA blood in a microhematocrit capillary tube. The packed cell volume (PCV) is the percentage of the column made up of red cells. The buffy coat is the thin white layer of leukocytes and platelets above the red cells. The plasma above is placed on a refractometer to read the total protein (total solids). Together, PCV/TP gives a fast read on red-cell mass and protein status.

Why does urine pH matter for crystals?

Crystal solubility depends on pH. Struvite crystals precipitate in alkaline urine, while calcium oxalate crystals form in acidic-to-neutral urine. Knowing the pH lets you predict and interpret which crystal type you are likely to see, which is why pH and the sediment exam are always read together.

How is the laboratory domain weighted on the VTNE?

Laboratory Procedures is one of the official 9 AAVSB VTNE domains, so it makes up a meaningful share of the roughly 170 scored multiple-choice questions on the exam. Domain weightings are set by the AAVSB and can be revised, so confirm the current blueprint percentages on aavsb.org or in the VTNE Candidate Handbook before you build your study plan.

Ready to lock in the Laboratory Procedures domain? Start your free VTNE trial and drill Laboratory questions, flashcards, and full timed practice exams in one place.