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Clinical Pathology  

Clinical Pathology

Flags for Clinical Pathologist Review of CBCs

By Ashleigh Newman

Ever wonder what happens to the blood sample you submitted for a complete blood count (CBC) to the Cornell Clinical Pathology Laboratory? Are you confused why your patient’s blood smear was or was not reviewed by a clinical pathologist? Spurred on by the resident research project of Dr. Ashleigh Newman in collaboration with research mentor and clinical pathologist Dr. Erica Behling-Kelly and clinician and Veterinary Information Network (VIN) consultant Dr. Mark Rishniw, these questions are going to be answered!

Drs. Newman, Behling-Kelly, and Rishniw’s research titled, “Red blood cell morphology: is there discordance between clinical pathologists and clinicians?” which was presented at the 2013 American College of Veterinary Pathology / American Society of Veterinary Clinical Pathology Annual Meeting and published as an Editor’s Choice article in the December 2014 issue of Veterinary Clinical Pathology, not only compared clinicians’ and clinical pathologists’ perceptions regarding the clinical utility of red blood cell (RBC) morphologic changes, but also identified areas of discordance and misunderstanding between these two groups. It was clear based on clinician responses, that there was confusion regarding what proportion of blood smears clinical pathologists review and what criteria the laboratory uses to determine which blood smears are reviewed. In an effort to put these research findings into real-life practice and improve our laboratory’s transparency, we’re going to tell you how CBCs and blood smears are handled at the Cornell Clinical Pathology Laboratory. Keep in mind that this is our policy, and different laboratories likely have different practices based on a multitude of factors, such as case load and personnel.

Once the samples have arrived at our laboratory and are accessioned by our front desk staff for a CBC or blood smear review, they are taken to our hematology section where our group of medical technologists and veterinary technicians handle the samples. Blood smears are made from every submitted EDTA tube. After the EDTA sample is run through our automated analyzer (ADVIA 2120, Siemens Healthcare Diagnostics Inc, Tarrytown, NJ), the ADVIA result print-out is attached to the submission paperwork and our standardized hematology worksheet. This paperwork is matched with the patient’s corresponding blood smear(s) (both submitted smear, if provided, and the smear made by us), and a complete blood smear examination is performed by one of our technicians. A blood smear examination involves a full evaluation of the feathered edge, a white blood cell (WBC) differential count, WBC morphologic evaluation, RBC morphologic evaluation, platelet estimate, and parasite check (see Many CBCs/blood smear examinations are ‘normal’ for that species or have straight-forward abnormalities (e.g. left shift, toxic change), which are reported out by our technicians. However, we also receive many abnormal CBCs with unusual or rare findings (e.g. circulating neoplastic cells, hemoparasites, etc.), necessitating a review by a clinical pathologist (CP). The table below is a complete list of flags that initiate a CP review. This list was formulated by a consensus of the Cornell CPs. It is also important to note that CPs approach a blood smear examination similarly to a cytology smear, therefore it is important as a clinician to provide a brief, clinical patient history on the submission form, which helps the CP make the most appropriate interpretation of the abnormal findings. As always, if you have questions regarding the results you receive from our laboratory, please call and we will be happy to discuss the findings further with you. Note, that we do not charge extra for this internal process of CP smear review. However, if you request a “Path Review” on the request form, we will charge an additional fee for a CP to review the smear. This fee for this smear review is $40.00.

Cornell University
Animal Health Diagnostic Center
Clinical Pathology Laboratory
Flags for Clinical Pathologist CBC/Blood Smear Review

White blood cells Pancytopenia
Degenerative left shift with no toxic change
Toxic change with no left shift
Left shift with no toxic change in a horse or cow
WBC > 30,000/ul in large animals
WBC > 50,000/ul in small animals
Mast cells – any in a cat, >3 in a dog
Absolute lymphocytosis in an animal >2yrs old
Blasts or other atypical cells
Very low neutrophil count
Questioning cell identification
Red blood cells Hct ≤ 15% any species or ≤ 20% in the horse and dog
Any nucleated RBCs in a horse
Large numbers (>20) of nRBCs in other species in the absence of regeneration (polychromasia)
Macrocytes in anemic horses
Spherocytes – review on first presentation or if patient getting worse
Agglutination – same as above
Parasites other than microfilaria (all species) and Leukocytozoon and Hemoproteus (birds)
Ovalocytes in a dog
Moderate to many siderocytes or prominent siderocytes
Heinz bodies in any species other than cat
Large Heinz bodies in a cat

Count <50,000/ul
Any time the automated counts are not matching the smear