Pathologist Blood Smear (CBC) Review Protocols

At CityU VDL all the blood smears are reviewed by our technologists. Cases that fulfill certain criteria are further reviewed by the clinical pathologist. Alternatively, there is the option of requesting a CBC with clinical pathologist review.

Criteria for clinical pathologist review:

Leukocytes:

• Pancytopenia
• Degenerative left shift with no toxic change or if questioning cell identification
• Toxic change with no left shift
• Left shift (>1% bands) with no toxic change in a horse or cow.
• WBC > 30x10⁹/L in large animals
• WBC > 50x10⁹/L in small animals
• Histiocytes seen
• Mast cells seen – any in a cat, >3 in a dog
• Absolute lymphocytosis in an animal >2yrs
• If there is an absolute lymphocytosis and the animal is less than 2yrs old, and the lymphocytes are small mature forms, there is no need to send for review since it is likely an epinephrine response.
• If the animal is over 2 yrs or there are any atypical lymphocytes seen, then send it for review.
• Blast cells or other atypical cells:
• Blasts: round cells with fine chromatin with or without nucleoli.
• Other leukocytes with abnormal morphology which may include:
• Abnormal granulation or inclusions
• Large cells – e.g. giant neutrophils
• Very low neutrophil count.
• Toxic change only in bands

Red Blood Cells:

• Anemia with HCT ≤ 15, or ≤ 20 in the horse and dog
• Any nucleated RBCs in a horse
• Large numbers (>20) of nucleated RBCs in other species in the absence of regeneration
• Hypochromasia
• Macrocytes in anemic horses
• Spherocytes
• Agglutination
• Parasites other than leukocytozoon, microfilaria and hemoproteus
• Ovalocytes in a dog
• Moderate to many siderocytes or very prominent siderocytes
• Heinz bodies in any species but a cat
• Large Heinz bodies in a cat

Platelets:

• Very low platelets - <50x10⁹/L when the count is not matching the smear
• Any time the counts are not matching the smear.