20 Laboratory Procedures Practice Questions & Answers

1. 1. You have filled, sealed, and spun a microhematocrit tube for a dog, and the owner in the exam room asks you what the packed cell volume means for her pet. What is the correct action?

   • A.Record the result and refer the owner's question to the veterinarian or credentialed technician✓ Answer
   • B.Compare the figure with the chart on the wall and tell the owner it is within normal limits
   • C.Read the column against the scale and tell the owner the figure and what it suggests
   • D.Tell the owner that no result is available until the sample is sent to the outside laboratory

   The NAVTA skills list assigns the assistant the verbs prepare and spin, with the tube evaluated by the veterinarian or veterinary technician. Running and recording a test is inside the assistant's role; assigning meaning to the number and communicating that meaning to a client is interpretation, which belongs to the veterinarian.

   Source: NAVTA Veterinary Assistant Essential Skills, Laboratory Procedures — microhematocrit tubes prepared and spun for evaluation by the veterinarian or veterinary technicianReport a problem with this question

2. 2. You set up a fecal flotation for a puppy with diarrhea, and while checking that the coverslip transferred cleanly you clearly see oval eggs on the slide. What should you do next?

   • A.Enter the finding in the record as a positive result and name the parasite you saw
   • B.Discard the slide and set up a second flotation before anyone else looks at the sample
   • C.Tell the owner that the puppy has worms so that treatment can be started right away
   • D.Leave the slide ready on the stage and ask the veterinarian or technician to examine it✓ Answer

   The official skill statement reads that the assistant sets up fecal flotations and direct smears for examination by the veterinarian or veterinary technician, and the list adds that individual species identification is not expected at the assistant level. Seeing structures on a slide is not the same as reading the slide for a result.

   Source: NAVTA Veterinary Assistant Essential Skills, Laboratory Procedures — fecal flotations and direct smears set up for examination by the veterinarian or veterinary technicianReport a problem with this question

3. 3. A urine sample is needed from a cat for bacterial culture, and the veterinarian asks you to get the room ready. Which statement correctly describes the collection method and your part in it?

   • A.A catheterized sample is preferred for culture because the catheter passes no resident bacteria
   • B.Any collection method is acceptable for culture as long as the container used is sterile
   • C.A voided free-catch sample is preferred for culture because no needle enters the bladder
   • D.Cystocentesis is preferred for culture, and the assistant restrains the patient for the procedure✓ Answer

   Bacteria in a cystocentesis sample can be attributed to the bladder, whereas voided and catheterized samples pick up organisms from the lower urogenital tract and can produce misleading culture growth. The NAVTA skills list assigns the assistant voided collection and supporting roles such as restraint, not the cystocentesis itself.

   Source: Merck Veterinary Manual, Urinalysis — urine collection methods and suitability for cultureReport a problem with this question

4. 4. A voided urine sample is collected first thing in the morning, but the veterinarian cannot look at it until the afternoon. How should the sample be handled in the meantime?

   • A.Refrigerate it in a sealed container and analyze it cold so that no crystals can dissolve
   • B.Freeze it in a sealed container so that bacterial overgrowth and cell breakdown are stopped
   • C.Refrigerate it in a sealed container and return it to room temperature before analysis✓ Answer
   • D.Leave it capped at room temperature so that the crystals and cells are not altered at all

   Urine is ideally examined within about 30 minutes; when that is not possible it may be refrigerated for up to about 24 hours. Refrigeration causes crystals to precipitate out of solution, so the sample is warmed back to room temperature before testing, while standing warm allows bacterial overgrowth and cell and cast breakdown.

   Source: Merck Veterinary Manual, Urinalysis — sample preservation, refrigeration, and crystal precipitationReport a problem with this question

5. 5. The veterinarian orders a complete blood count and a blood smear on a dog and asks you to stage the supplies. Which tube should you set out for the sample?

   • A.The lavender tube with EDTA, which holds the cells intact and preserves their morphology✓ Answer
   • B.The light blue tube with sodium citrate, which is filled to a fixed line for clotting tests
   • C.The gray tube with sodium fluoride, which stops the sugar in the sample from breaking down
   • D.The red tube with no additive, which lets the sample clot fully and then yields serum

   EDTA is the anticoagulant of choice for hematology because it keeps blood unclotted while preserving cell size and morphology well enough to count cells and read a smear. A clotted or serum tube gives no intact cell population to count, and the fluoride and citrate tubes are matched to glucose and coagulation testing respectively.

   Source: CLSI GP41, blood collection tubes and additives; MSD Veterinary Manual, Clinical HematologyReport a problem with this question

6. 6. A light blue tube drawn for a coagulation test comes back to the laboratory only about half full. Why is the sample not acceptable?

   • A.The cells shrink in the extra citrate, so the packed cell volume is falsely lowered
   • B.There is too little citrate for that volume, so the sample will clot inside the tube
   • C.Nothing is wrong with it, provided the tube is inverted gently a few extra times
   • D.The fixed ratio of blood to citrate is lost, so the coagulation result will be invalid✓ Answer

   A citrate tube contains a measured volume of liquid anticoagulant designed for a full draw, so the blood-to-citrate ratio only holds when the tube is filled to its line. Underfilling leaves excess citrate relative to plasma, which alters clotting times, and the underfilled tube is the classic rejected coagulation sample.

   Source: CLSI GP41, blood collection tubes and additives — sodium citrate tube fill requirementReport a problem with this question

7. 7. You are staging tubes for a draw that will fill a lavender EDTA tube, a light blue citrate tube, and a red serum tube. In which order should they be filled?

   • A.Red serum, then lavender EDTA, then light blue citrate
   • B.Light blue citrate, then red serum, then lavender EDTA✓ Answer
   • C.Lavender EDTA, then red serum, then light blue citrate
   • D.Lavender EDTA, then light blue citrate, then red serum

   The standard order of draw exists to stop additive from one tube being carried on the needle into the next tube. Citrate is drawn early so the coagulation ratio is protected, and EDTA is drawn after the serum tube because carried-over EDTA binds calcium and adds potassium, which distorts chemistry results.

   Source: CLSI GP41, order of blood draw tubes and additivesReport a problem with this question

8. 8. A chemistry sample you helped collect is rejected because the serum is pink from hemolysis. Which handling step during collection most likely caused it?

   • A.The tube was filled to its marked line and then inverted gently end over end
   • B.The venipuncture site was wiped with alcohol and allowed to dry before the stick
   • C.The tube stood upright in a rack at room temperature while the sample clotted
   • D.The blood was forced through the needle into the tube and the tube was shaken hard✓ Answer

   Hemolysis is red cells rupturing and releasing their contents into the plasma or serum, and mechanical shear is the cause the assistant controls. Pushing blood through a narrow needle and shaking the tube both shear cells, which is why the needle is removed and tubes are mixed by gentle inversion instead.

   Source: MSD Veterinary Manual, Clinical Hematology — sample collection and causes of hemolysisReport a problem with this question

9. 9. You are loading a filled and clay-sealed microhematocrit tube into the microhematocrit centrifuge. Which description matches correct technique?

   • A.Sealed end outward toward the rim, with a second tube opposite it to balance the load✓ Answer
   • B.Sealed end inward toward the center, with a second tube opposite it to balance the load
   • C.Both ends of the tube left open, with a second tube opposite it to balance the load
   • D.Sealed end outward toward the rim, with the tube spun alone in an otherwise empty rotor

   Centrifugal force pushes the contents toward the rim, so the sealed end must face outward or the blood is driven out of the tube. Every centrifuge load is also balanced with an opposing tube of equal weight, because an unbalanced rotor damages the instrument and can break tubes and aerosolize the sample.

   Source: MSD Veterinary Manual, Clinical Hematology — packed cell volume by microhematocrit centrifugationReport a problem with this question

10. 10. An owner brings in a thin smear of feces on a cotton swab and asks for a flotation on a dog that has had soft stool for a week. What is the correct response?

    • A.Ask for a larger sample, because too little feces produces a false negative result✓ Answer
    • B.Add extra flotation solution, because the added volume compensates for the small sample
    • C.Run the flotation as it is, because sensitivity does not depend on the amount of feces
    • D.Set up a direct smear only, because a swab holds enough feces for that test alone

    Flotation sensitivity depends on how much feces is examined, because eggs are shed unevenly and a tiny sample may contain none. Published guidance scales the amount to consistency, roughly 1 gram of formed feces, 2 grams of soft feces, 4 grams of slurry, and 6 grams or more of liquid feces.

    Source: CAPC fecal exam procedures — recommended fecal sample amount by consistencyReport a problem with this question

11. 11. A fecal sample arrives at the end of the day and cannot be processed until the next morning. How should it be stored overnight?

    • A.Frozen in a sealed container, because freezing halts all further parasite development
    • B.In a warm incubator in a sealed container, because warmth keeps organisms recognizable
    • C.Refrigerated in a sealed container, because freezing distorts protozoal organisms✓ Answer
    • D.At room temperature in a sealed container, because chilling ruptures the parasite eggs

    Fresh feces examined promptly is best; when that is not possible the sample is refrigerated in a sealed, labeled container. Freezing damages the delicate morphology of protozoal cysts and trophozoites, while warm storage lets certain nematode eggs develop and hatch, which makes the material harder to interpret.

    Source: CAPC fecal exam procedures — specimen handling and storage before examinationReport a problem with this question

12. 12. The veterinarian suspects Giardia in a puppy and asks you to prepare the flotation solution. Which solution is appropriate and on what basis?

    • A.Saturated sodium chloride, because salt best preserves the shape of the delicate cysts
    • B.Saturated sugar solution, because its high specific gravity floats the delicate cysts
    • C.Plain tap water, because the delicate cysts are lighter than water and rise to the top
    • D.Zinc sulfate, because a higher specific gravity would distort the delicate cysts✓ Answer

    Flotation works because parasite eggs and cysts are less dense than the solution and rise while heavier debris sinks, with working solutions in roughly the 1.18 to 1.30 specific gravity range. Zinc sulfate sits at the low end of that range, which floats cysts without the osmotic collapse that high-density sugar and salt solutions cause.

    Source: CAPC fecal exam procedures — flotation solutions and specific gravity rangeReport a problem with this question

13. 13. You are asked to set up a direct fecal smear alongside the flotation for a dog with watery diarrhea. How is the smear prepared and what is it for?

    • A.A thick layer of feces with saline, to raise the number of eggs present on the slide
    • B.A small amount of feces with stain and no fluid, to fix the organisms onto the slide
    • C.A small amount of feces with saline, to look for motile protozoa and for larvae✓ Answer
    • D.A small amount of feces with flotation solution, to concentrate the eggs on the slide

    The direct smear uses saline because the point is to keep organisms alive and moving so motile protozoa and larvae can be seen, which a flotation solution would kill and distort. The smear examines only a tiny amount of feces, so it is low in sensitivity and supplements a flotation rather than replacing it.

    Source: CAPC fecal exam procedures — direct smear technique and its limitationsReport a problem with this question

14. 14. You have just made a blood smear and are about to stain it with a three-step quick stain. What is the correct handling and dip sequence?

    • A.Air dry the smear fully, then the blue solution, then the red, then the fixative
    • B.Stain the smear while still wet, then the fixative, then the red, then the blue
    • C.Air dry the smear fully, then the fixative, then the red solution, then the blue✓ Answer
    • D.Heat fix the smear over a flame, then the red solution, then the blue, then rinse

    The smear must dry in air before the alcohol fixative touches it, because fixing a wet film traps water and creates artifact that ruins cell detail, and heat fixing cooks and destroys blood cell morphology outright. The quick stain is then used in its designed order: fixative, the red-orange solution for cytoplasm, then the blue solution for nuclei.

    Source: MSD Veterinary Manual, Clinical Hematology — blood smear preparation and Romanowsky-type stainingReport a problem with this question

15. 15. A client brings in an adult parasite removed from her dog, and you are sorting it into a group before the veterinarian looks at it. Which feature separates an adult tick from an adult flea?

    • A.The tick is flattened side to side; the flea is flattened top to bottom
    • B.The tick has eight legs and an unsegmented body; the flea has six legs✓ Answer
    • C.The tick has wings once mature; the flea is wingless and jumps strongly
    • D.The tick has six legs and an unsegmented body; the flea has eight legs

    Leg count and body plan are the reliable group-level discriminator: ticks and mites are arachnids with eight legs as adults, while fleas and lice are insects with six. The skills list states that identifying the individual species is not expected at the veterinary assistant level, so sorting to group is the correct depth.

    Source: NAVTA Veterinary Assistant Essential Skills, Laboratory Procedures — differentiate between the mite, louse, flea, and tickReport a problem with this question

16. 16. You place a fecal flotation slide on the microscope stage and need to bring it into focus. What is the correct sequence?

    • A.Start on the oil objective with a drop of oil and use the coarse adjustment throughout
    • B.Start on the lowest objective, focus coarsely, then sharpen with the fine adjustment✓ Answer
    • C.Start on the highest dry objective, focus coarsely, then sharpen with the fine adjustment
    • D.Start on the lowest objective, focus finely, then switch to the coarse adjustment

    The lowest objective gives the widest field, which makes the specimen easy to find, and it leaves the most clearance between lens and slide so the coarse adjustment is safe to use. On higher objectives the working distance is very small, so coarse focusing can drive the lens into the coverslip and break the slide or scratch the lens.

    Source: MSD Veterinary Manual, Diagnostic Procedures for the Private Practice Laboratory — microscope use in the practice laboratoryReport a problem with this question

17. 17. You have finished reading a stained smear under the oil immersion objective and are shutting down the laboratory. How should the microscope be cared for?

    • A.Wipe the oil off the objective with gauze dampened with the surface disinfectant
    • B.Wipe the oil off the objective with a paper towel and alcohol, which cuts oil fastest
    • C.Leave the oil on the objective, since it dries into a protective film over the glass
    • D.Wipe the oil off the objective with lens paper and lens cleaner before it is stored✓ Answer

    Immersion oil left on the lens hardens and clouds the optics, so it is removed at the end of every session. Only lens paper and a cleaner made for optics are used, because paper towel and gauze are abrasive enough to scratch the coating and solvents such as alcohol and disinfectants can dissolve the cement holding the lens elements.

    Source: MSD Veterinary Manual, Diagnostic Procedures for the Private Practice Laboratory — care and maintenance of the practice microscopeReport a problem with this question

18. 18. You realize that a laboratory result you wrote by hand went into the wrong patient's record. How should the entry be corrected?

    • A.Cover it with correction fluid, then add the correct entry in the space it leaves
    • B.Draw a single line through it, then add the correction with your initials and the date✓ Answer
    • C.Write over the entry in darker ink, so that the correct entry is the readable one
    • D.Erase the entry completely, then add the correct entry so the page stays legible

    The medical record is a legal document, so the history of what was written has to remain visible and attributable. A single strike-through leaves the original entry readable while showing that it was corrected, and the initials and date show who made the change and when; erasing, whiting out, or overwriting destroys that trail.

    Source: NAVTA Veterinary Assistant Essential Skills, Laboratory Record Keeping; AVMA guidance on veterinary medical records as legal documentsReport a problem with this question

19. 19. A blood sample is being packed to go to an outside reference laboratory. What must be true before the package leaves the clinic?

    • A.The tube label and the submission form must match and identify the same patient✓ Answer
    • B.The tube may travel unlabeled, provided the submission form identifies the patient
    • C.The tube label may carry initials only, since the form already carries the full name
    • D.The submission form may follow later, once the laboratory has logged the sample in

    Once a tube leaves the clinic, the label is the only thing tying that specimen to the animal it came from, so identity must never rest on paperwork that can be separated from the tube. Samples are labeled at the point of collection with patient and client identification, the date and time, and the sample type, and the submission form must agree with the label.

    Source: NAVTA Veterinary Assistant Essential Skills, Laboratory Record Keeping — accurate recording and filing of laboratory reports and outside submissionsReport a problem with this question

20. 20. An in-house analyzer prints a result that does not fit a patient who looks entirely well, and you notice the control material in the kit expired last month. What should you do?

    • A.Record the printed result as it stands and let the veterinarian sort out the discrepancy
    • B.Record the result but write beside it that the analyzer has been unreliable all day
    • C.Replace the expired control, repeat the run, and tell the veterinarian what happened✓ Answer
    • D.Discard the printout and repeat the test without mentioning that a first run occurred

    Quality control exists so that a result can be trusted before it enters the record: expired control material no longer proves the analyzer is performing correctly, so a result run against it is unverified. The assistant's part is to remove expired items, repeat the test under valid conditions, and report the situation, while the veterinarian decides what the result means.

    Source: NAVTA Veterinary Assistant Essential Skills, Laboratory Record Keeping — remove expired items; quality-control principles for in-house analyzersReport a problem with this question

Practice questions based on the NAVTA veterinary assistant skill categories and standard veterinary assisting practice. This site is not affiliated with or endorsed by NAVTA. Note that the Approved Veterinary Assistant credential requires completing a NAVTA-approved training program before you may sit the exam — this bank is study material, not a substitute for that program, and it cannot cover the hands-on skills your program assesses in a clinic. What an assistant is permitted to do is set by your state's veterinary practice act and by what the supervising veterinarian delegates, so nothing here should be read as authorising a task where you work. About the AVA credential →