Laboratory Procedures practice questions

Answer: A) Increased bacterial numbers and a higher urine pH

Urine left at room temperature grows bacteria, becomes more alkaline as bacteria break down urea, and loses casts and cells to breakdown. It should be analyzed promptly or refrigerated.

• ACorrect. Bacteria multiply in urine kept at room temperature. Many of them break down urea into ammonia, which makes the urine more alkaline (higher pH).
• BIncorrect. With delay, casts dissolve and red and white blood cells break down, especially as the pH rises. The counts in the sediment go down, not up.
• CIncorrect. Without refrigeration, bacteria grow rather than die off. Their breakdown of urea tends to raise the pH rather than lower it.
• DIncorrect. Glucose doesn't build up in stored urine. Growing bacteria and cells use it up, so a delay can falsely lower the glucose reading.

Answer: A) The monolayer just behind the feathered edge, where red cells are close together but barely overlap

Differential counts and cell shape assessment are done in the monolayer, just behind the feathered edge, where cells are evenly spread and not distorted. The feathered edge and side edges are only scanned for platelet clumps and large cells.

• ACorrect. In the monolayer, cells lie in a single, evenly spread layer and keep their normal shape. This allows accurate identification and a representative count.
• BIncorrect. In the thick area, cells pile on top of each other and look shrunken, which makes leukocytes hard to identify.
• CIncorrect. The feathered edge should be scanned for platelet clumps and large or abnormal cells. Cells there are often distorted or broken, and large cells collect there, so counting there skews the differential.
• DIncorrect. Larger leukocytes tend to gather along the edges, so counting only there would give too many of them. A count from the monolayer is more representative.

Answer: C) More than 90% superficial and anuclear (cornified) epithelial cells

Estrus is identified when more than 90% of vaginal epithelial cells are cornified superficial or anuclear cells. Proestrus shows red cells with mixed epithelial cells, diestrus shows an abrupt return of intermediate and parabasal cells and neutrophils, and anestrus shows sparse non-cornified cells.

• AIncorrect. This describes proestrus. Red cells are present, and the proportion of superficial cells rises gradually but hasn't yet reached the estrus level.
• BIncorrect. This describes early diestrus. Superficial cells drop suddenly, intermediate and parabasal cells take over, and neutrophils appear again.
• CCorrect. High estrogen causes cornification of the vaginal epithelium. An estrus pattern is defined as more than 90% superficial or anuclear squamous cells, with or without red cells. This pattern helps time breeding.
• DIncorrect. This describes anestrus. The smear has few cells, mainly non-cornified parabasal and intermediate cells.

Answer: A) How well the insulin dose and timing are working

• ACorrect. Glucose is checked every 1 to 2 hours.
• BIncorrect. It measures glucose.
• CIncorrect. It measures glucose.
• DIncorrect. It measures glucose.

Answer: C) Buccal mucosal bleeding time (BMBT)

BMBT tests primary hemostasis by timing how long a small cut in the inner lip bleeds. It is prolonged with platelet function defects such as von Willebrand disease. PT and ACT test clotting factors, and a platelet count measures number, not function.

• AIncorrect. PT checks the extrinsic and common clotting-factor pathways (secondary hemostasis). It does not test how well platelets form a plug.
• BIncorrect. ACT is a screening test for the intrinsic and common clotting-factor pathways (secondary hemostasis). It does not test platelet function.
• CCorrect. BMBT measures how long a small standard cut in the inner lip takes to stop bleeding. That depends on platelets forming a plug, so the time is prolonged in von Willebrand disease and other platelet function problems.
• DIncorrect. A platelet count measures how many platelets there are, not how well they work. Dogs with von Willebrand disease often have normal counts.

Answer: A) Heartworm infection and flea allergy dermatitis

Eosinophilia is classically caused by parasites (especially helminths) and by allergic or hypersensitivity conditions. Corticosteroid excess lowers eosinophils, and bacterial infection mainly raises neutrophils.

• ACorrect. Eosinophils typically rise with helminth (parasite) infections and with allergic or hypersensitivity disease. Heartworm infection and flea allergy dermatitis are classic veterinary examples.
• BIncorrect. Too much corticosteroid, whether given as a drug or produced by the body, causes a stress leukogram. That pattern lowers eosinophils (eosinopenia) rather than raising them.
• CIncorrect. Bacterial and pus-forming conditions such as pyometra mainly cause a neutrophilia, often with a left shift. They don't cause an eosinophilia.
• DIncorrect. Blood loss and hemolysis mainly affect the red cell values (anemia, often with a regenerative response). They aren't a typical cause of increased eosinophils.

Answer: B) Struvite

• AIncorrect. Those look like envelopes.
• BCorrect. Magnesium ammonium phosphate.
• CIncorrect. Those are ammonium biurate spheres.
• DIncorrect. Those are hexagonal.

Answer: A) The flotation solution has a higher specific gravity than the eggs and oocysts, so they rise to the surface

Fecal flotation concentrates parasite stages whose specific gravity is lower than the solution's, so they rise to the coverslip. Dense eggs, such as many fluke eggs, do not float in standard solutions and are found by sedimentation.

• ACorrect. Flotation works because the solution (usually about 1.20–1.35) is denser than most nematode eggs and coccidian oocysts. Those stages are buoyant and rise to the meniscus and coverslip, while heavier debris settles.
• BIncorrect. This reverses the principle. Stages denser than the solution sink, which is why dense eggs, such as many fluke eggs, need a sedimentation technique instead.
• CIncorrect. Flotation solutions are not meant to dissolve eggshells. Eggs rise because they are less dense than the solution. Leaving a sample in solution too long can actually distort eggs.
• DIncorrect. Flotation solutions are denser than water (specific gravity above 1.0). Most parasite eggs sink in plain water, which has a specific gravity of 1.000.

Answer: A) Kidney tubule damage or disease

• ACorrect. They form in the tubules.
• BIncorrect. Many casts are abnormal.
• CIncorrect. Casts form in the kidney.
• DIncorrect. Casts form in the kidney.

Answer: A) Place a capped tube holding an equal volume of water in the slot directly opposite the sample

A centrifuge must be balanced before it runs: tubes of equal weight go directly opposite each other, using a water-filled balance tube when needed. Tubes stay capped to prevent aerosols.

• ACorrect. A balance tube of equal weight placed opposite the sample spreads the load evenly around the rotor. This prevents vibration, damage to the rotor and centrifuge, and poor separation.
• BIncorrect. Even one tube makes the load uneven at high speed. The rotor must be balanced no matter how many tubes are loaded.
• CIncorrect. Tubes should stay capped while spinning. Loose or open caps let the sample leak and form aerosols, which puts staff at risk if the sample is infectious.
• DIncorrect. An empty tube in the next slot does not offset the sample's weight. The counterweight must be equal in weight and sit directly opposite the sample.