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Cytology

The ideal cytology sample has a good harvest of cells that are well-preserved and wellspread on the slide. The cytologist then has enough material to determine if the sample is representative, and enough cell detail to establish the origin and significance of the cells present.

General Guidelines
  • All cytology submissions should include direct, air-dried preparations, regardless of the type of sample. The only exceptions are urine and CSF (see below).
  • Use glass slides with a frosted end, and label each slide with the owner's name and site sampled using a pencil or indelible marker. Do not label slides with adhesive tape, transparent tape, or sticky labels since these become unreadable during the staining process. If more than one site is sampled, use separate slides for each site and label each slide accordingly. Indicate the sites on the requisition form.
  • Rapid air-drying of samples provides ideal fixation. Wave slides quickly in the air (do not blow on slides). Wet fixation (e.g. Cyto-fix) is acceptable, but provides no advantage over rapid air fixation. Do not heat fix slides or use formalin, since either will render the sample useless.
  • Do not stain slides prior to submission. In-clinic stains are inappropriate for some samples (e.g. mast cell tumours) and can interfere with interpretation.
  • Always provide complete patient signalment including species, breed, age, and gender. A brief concise history, including clinical signs and gross appearance of lesions is extremely helpful.
  • Submit slides in sturdy cardboard carrier or plastic slide holder. Always keep cytology specimens well separated from histology submissions, since fumes from the formalin container can affect the staining properties of the cytological material.

Common Techniques for Making Cytology Smears
Blood Smear Technique: used for fluids of uniform consistency and most fine needle aspirates of solid tissue
  1. Place a small drop of aspirated material on a clean glass slide.
  2. Using a second slide as a spreader, hold it against the first slide, drawing back to briefly touch the droplet of sample.
  3. Move the second slide quickly and smoothly along the length of the first slide, dragging a thin layer of the material behind.
Squash or Crush Preparation: Used for fluids with suspended solid particles, and for thick or viscous material
  1. Place a small amount of sample on a clean glass slide.
  2. Place a second slide at right angles to the first so that it lies flat over the sample.
  3. Without exerting any downward pressure, pull the top slide gently along the bottom slide and lift off, creating a broad smear on both slides. (Note: Excessive pressure on the top slide will lead to widespread cell rupture and loss of diagnostic value.)
Sample Submission

Cavity fluid
Make air-dried smears immediately and send the remaining fluid in lavender and plain red top tubes for cell count, protein content, and additional smear preparation. Special tests can be run on effusions to rule out pancreatitis, uroperitoneum, chylous effusion, FIP, etc. If sedimented smears are prepared in-clinic, label the slides accordingly. Do not submit syringes of fluid with needles attached.

Cystic mass
Fluid aspirated from a cystic mass is prepared like cavity fluid. In addition, a fine needle aspiration of the mass "wall", underlying tissue or solid areas within the mass is recommended. Label slides clearly if both fluid and solid material is submitted.

Urine
Collect free flow or catheterized sample. Send half of the sample as whole urine in a sterile container, and centrifuge the remaining urine. Following sedimentation, draw off the supernatant and resuspend the button of cells by gently flicking the tube with a finger.

Prepare air-dried smears of the unstained sediment.

Joint fluid
Always send air-dried smears. Smears made in the laboratory from submitted fluid are invariably inferior. If joints are effusive and extra fluid can be aspirated easily, extra fluid should be submitted in lavender and red top tubes for cell count and protein content. Blood contamination may result in a non-diagnostic sample and should be avoided. In cases of polyarthropathy, submit multiple joint taps and label slides accordingly.

Cerebral spinal fluid (CSF)
Centrifuge sample within 1 hour of collection and submit an air-dried smear of sedimented CSF for examination. Whole CSF fluid is sent for total cell count, protein content, and red blood cell count. Please call VITA-TECH for details on making a sedimentation chamber.

Lymph nodes
If peripheral lymphadenopathy is present, aspirate multiple enlarged nodes, especially prescapular, popliteal, and inguinal nodes if affected. Place a small amount of aspirated lymphoid material on a slide, spread it gently using a crush or blood smear technique, and rapidly air-dry. Smears that are too thick or in which all the lymphocytes have ruptured cannot be interpreted.

Bone marrow
Prepare air-dried smear by placing a large droplet of the aspirated bone marrow on a slide and tilting the slide to allow excess blood to drain away before making a squash preparation of the granules adhering to the slide. Send excess bone marrow material in a lavender top tube. Always include a sample of peripheral blood in a lavender top with each bone marrow submission. If a core biopsy is submitted in formalin, package cytology and histology samples separately to avoid exposing smears to formalin fumes.

Ultrasound guided aspirates
Be careful of Ultrasound gel since it can ruin a specimen.
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