Dos and donts when preparing veterinary clinical pathology samples

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You see a cytologic specimen or a blood smear from a veterinary patient and need to submit it to the reference laboratory. Have you followed protocol correctly to ensure the lab can get the best read possible?

In her recent Fetch dvm360 session on submitting clinical pathology samples to reference laboratories, Natalie Hoepp, DVM, MS, DACVP, covered some of the more important dos and don'ts for prepping those samples correctly. Use this checklist to help ensure you have the best sample possible.

Before we get started, a special callout: The most important thing you should do every time no matter the sample? Label everything with the patient ID, site and date!

For cytologic specimens

DO

Take and prepare the sample correctly

In her session, Dr. Hoepp told attendees to follow these guidelines when it comes to getting that perfect sample and ensuring a seamless process:

• Aspirate without using suction; instead go for the “woodpecker technique.”

• Use care to avoid lysing cells, especially in lymphoma suspects.

• Spread the sample across the slide.

• Allow slides to air-dry at room temperature.

• Submit unstained, unfixed slides.

• Make a few direct preparations of fluids (except for cerebrospinal fluid [CSF]) prior to transport and send slides and fluid to the reference lab.

• If fluid is a split sample for cytologic exam and culture, denote this clearly and include separate tubes to avoid inadvertent use of the wrong sample. (Note: Two submission forms will decrease confusion in the lab.)

• Make line preps of fluids (except for CSF).

Get your request in order

You need to know exactly what testing to order-and, Dr. Hoepp emphasizes, mark the submission form correctly! She says you should also:

• Complete the submission form yourself-do not delegate this particular task.

• Double-check your work! An error-free submission form will avoid delays in processing.

• Include pertinent history in legible handwriting.

• Describe the mass using specific details, such as distinct location (e.g. cutaneous, intrathoracic, bladder wall near the trigone), interaction with surrounding tissues (fixed, mobile, possibly arising from … ), palpable composition (firm, soft with a firm central area, fluctuant), and size, shape, color, presence or absence of hair, gross appearance of aspirated material, duration, response to treatment, clinical suspicion and any other relevant details.

If you're not sure what you need or how to ship, call the reference lab for guidance.

DON'T

Dr. Hoepp also has a list of things for practitioners to avoid when submitting cytologic specimens. Remember to never ...

• Submit slides in a slide case and label only the outside of the container. (Remember: Label each slide and tube!)

• Leave information out to avoid “biasing the pathologist.” Giving incomplete information gets you worse results.

• Ship slides in the same package with biopsy specimens due to the risk of formalin artifacts appearing on slides. (The fumes alone cause this-not just spills!)

• Heat-fix, pre-stain, coverslip or package slides directly against ice packs, refrigerate slides, or leave them outside in very cold temperatures.

• Ask that additional testing be completed “if indicated” by the cytologic exam results, which puts further testing at the pathologist's discretion instead of the clinician's.

For CBCs and blood smear reviews

DO

Take and prepare the sample correctly

Getting that perfect blood smear is a work of art, Dr. Hoepp says. Follow these steps to make sure all of your samples are masterpieces:

• Let the EDTA tube vacuum pull the sample in without pushing it through the needle too aggressively-that increases the risk of clumps and clots, Dr. Hoepp says.

• Fill EDTA tubes to the amount they are designed to draw, not to the top of the label or other inconsistent markers.

• Immediately and gently invert the tube 10 times to mix blood and anticoagulant.

• Make a blood smear at the time of sample acquisition and let it air-dry for 20 minutes prior to shipment. (Dr. Hoepp says it doesn't have to be a great smear-you just want a few representative areas for comparison.)

Get your request in order

Dr. Hoepp told attendees to make sure they request the correct type of complete blood count (CBC) analysis, paying attention to the different variations. She also stresses that veterinary professionals should:

• Request a pathologist review if the patient is sick, anemic, has a history of leukemia or hematopoietic neoplasia, or is being monitored during treatment.

• Include patient history and previous bloodwork for the pathologist to review. (Note: Think that information is “in the system” already? Dr. Hoepp says it might not be, or they might not be able to access it. Include it!)

• Remember: A patient-side test for tick-borne disease can be negative in acute rickettsial disease, warranting smear review for morula if this is suspected (e.g. the patient is experiencing fever or thrombocytopenia or has been exposed to ticks).

DON'T

• Give clients the option to skip baseline bloodwork. This is your liability insurance!

• Put blood smear slides in the refrigerator.

• Put the sample and slides directly against ice packs, pack with dry ice or leave the pickup box in freezing temperatures for too long.

• Heat-fix, fix in methanol or stain blood smears prior to transport

The best samples will get you the best results, Dr. Hoepp reminds attendees. Preparing your orders carefully and double-checking your work in addition to labeling every last slide and tube might feel like it's taking a long time, but you'll win out in the end by avoiding delays from the reference lab due to confusion or errors. Go forth and prepare with confidence!