Laboratory Procedures makes up 9% of the VTNE — roughly 18 questions. The domain covers in-clinic diagnostics from sample collection and handling to CBC interpretation, urinalysis, fecal analysis, and basic clinical chemistry. These are core daily skills for every vet tech, and the VTNE expects both procedural competence and the ability to recognize abnormal results.
9% of the VTNE — approximately 18 questions. Allocate roughly 9% of your total study hours here to mirror the exam's weighting.
Know the normal reference ranges for the most common CBC and chemistry analytes — not as memorized numbers, but as ranges you can reason about. Then practice identifying abnormal values and the clinical conditions they suggest. A PCV of 18% in a dog: what does that tell you, and what do you do next?
Sample Collection & Handling
EDTA (purple top): CBC, blood smear. Heparin (green): chemistry, blood gas. Serum separator (gold/red): serology, chemistry. Citrate (blue): coagulation panels; 9:1 blood:anticoagulant ratio critical. Urine: cystocentesis is gold standard for culture; catheter or free-catch for routine UA. Refrigerate samples if not run immediately; spin serum separator tubes within 30–60 minutes.
Blood Smear Prep & Staining
Push technique: 2 drops of blood, spreader slide at 30–45° angle, smooth push to thin feathered edge. Diff-Quik: three-step rapid stain — fixative, eosinophilic dye, basophilic dye. Wright-Giemsa: more morphologic detail. Evaluate smear at feathered edge for RBC morphology; monolayer for WBC differential.
CBC Components
RBC count, hemoglobin (Hgb), PCV/HCT, MCV, MCHC, MCH (indices for classifying anemia). WBC total and differential. Platelet count and estimate. PCV: spin hematocrit tubes 5 min; read buffy coat (white = WBC), plasma color (icteric, lipemic, hemolyzed).
Hematology Values (RBC/WBC/Hgb/HCT/Platelets)
Dog reference ranges (approximate): PCV 37–55%, Hgb 12–18 g/dL, RBC 5.5–8.5 × 10⁶/µL, WBC 6,000–17,000/µL, platelets 200,000–500,000/µL. Cats run lower PCV (24–45%). Know when to flag: PCV < 20% = significant anemia requiring workup; WBC > 30,000 = possible infection, leukemia, or stress.
Differential Cell ID
Neutrophils (most common WBC, multi-lobed nucleus, pink cytoplasm), lymphocytes (small, round dark nucleus, scant cytoplasm), monocytes (largest, kidney-shaped nucleus, gray cytoplasm), eosinophils (bilobed nucleus, pink-red granules), basophils (dark purple granules, rare). Band neutrophils = left shift (regenerative response to infection).
Urinalysis (Physical/Chemical/Micro)
Physical: color (pale = dilute, dark yellow/orange = concentrated or bilirubinuria), clarity, specific gravity (refractometer: dog 1.015–1.045, cat 1.035–1.060). Chemical: dipstick — protein, glucose, ketones, bilirubin, blood, pH, nitrite. Microscopic: casts (granular, cellular, hyaline), crystals (struvite, oxalate, urate), bacteria, WBCs, RBCs.
Fecal Analysis & Parasitology
Direct smear: quick, detects motile protozoa (Giardia trophozoites), immediate. Fecal float: concentration technique for helminth eggs and coccidian oocysts. Common float solutions: sodium nitrate (SG 1.33), zinc sulfate (preferred for Giardia cysts, SG 1.18), sugar solution. Centrifugal flotation more sensitive than passive float.
Flotation & Wet-Mount
Passive flotation: 10–15 minute stand time. Centrifugal: 10 min at 400 × g; recover surface film with coverslip. Wet mount: saline wet prep for motility; Lugol's iodine stain for protozoan detail. Baermann technique for lungworm larvae.
Common Parasite ID
Know egg morphology: Toxocara (dog roundworm: thick, pitted shell, dark center), Trichuris vulpis (whipworm: football with polar plugs), Ancylostoma (hookworm: thin shell, segmented interior). Giardia cysts: oval, 4 nuclei. Coccidia oocysts: small, oval. Dipylidium proglottids: rice-like segments in feces.
Quality Control & Reference Ranges
Run controls daily on analyzers; document control results. Know high and low control ranges; results outside range = repeat or send to reference lab. Reference ranges are species and age-dependent; neonates and geriatrics may differ significantly.
Microscopy
Low power (10×): scan slide, locate areas of interest. High-dry (40×): cell identification, cast and crystal counting. Oil immersion (100×): differential cell count, bacteria identification, RBC morphology. Calibrate ocular micrometer for crystal and parasite sizing.
Clinical Chemistry Basics
Key analytes: BUN/creatinine (renal), ALT/AST (hepatic, ALT is liver-specific in dogs/cats), ALP (liver and bone), total protein/albumin (nutritional, hepatic), glucose (pancreatic endocrine), electrolytes (Na, K, Cl). Lipemia, hemolysis, and icterus cause assay interference — note sample quality on report.
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Frequently Asked Questions
What tube colors are tested on the VTNE for blood collection?
EDTA (purple/lavender): CBC and blood smears. Heparin (green): plasma chemistry. Serum separator (gold or red-gray): serum chemistry and serology. Citrate (blue): coagulation profiles. Mixing ratio for citrate is 9 parts blood to 1 part anticoagulant.
What fecal float solution is best for Giardia cysts on the VTNE?
Zinc sulfate centrifugal flotation (specific gravity 1.18) is the preferred method for recovering Giardia cysts, as their lighter density can cause them to collapse or distort in high-SG solutions like sodium nitrate.
What is a left shift and when does it occur?
A left shift refers to increased numbers of immature neutrophils (band neutrophils) in peripheral blood. It occurs when the bone marrow releases neutrophils before full maturation, typically in response to severe bacterial infection or significant inflammation. A regenerative left shift (band count exceeds mature neutrophils) indicates a more severe response.
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