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Hematologic numerical results provide red flags as to the presence of underlying disease.
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Examination of a blood smear for morphologic changes, for example, left shift, toxic change, abnormal cells, or infectious agents, is a crucial part of a diagnostic workup; do not rely only on numbers alone.
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Interpret laboratory data with pertinent clinical information (history, physical examination, and diagnostic imaging).
Hematology Red Flags: The Value of Blood Smear Examination in Horses
Section snippets
Key points
Blood is our window into the animal. From clinical pathologic results, we can
Case 1
A 21-year-old Quarter Horse mare presented with fever, inappetence, and limb edema. The mare was tachycardic, tachypneic, and febrile, with injected sclera, hyperemic, and tacky mucous membranes, prolonged capillary refill time, and skin tenting. Pertinent results are shown.Case 1: Hemogram Test Name Result Empty Cell Reference Interval Units Hematocrit (HCT) 86 (H) 34–46 % Red blood cells (RBC) 15.8 (H) 6.6–9.7 × 106/μL Mean cell volume (MCV) 54 43–55 fL Mean cell hemoglobin concentration (MCHC) 34 34–37 g/dL White blood cells
Case 2
A 12-year-old Quarter Horse gelding presented with a 3- to 4-day history of colic, fever, and anorexia. The horse had been given penicillin 3 weeks earlier for a leg laceration, which was switched to trimethoprim-sulfonamides. The gelding was quiet, tachycardic, and febrile, with icteric mucosa and the urine was dark red. Pertinent results are shown.Case 2: Hemogram Test Name Result Empty Cell Reference Interval Units HCT 17 (L) 34–46 % RBC 6.5 (L) 6.6–9.7 × 106/μL MCV 53 43–55 fL MCHC 37 34–37 g/dL Red cell distribution width
Case 3
A 15-year-old Hanoverian gelding presented with acute ataxia. Cerebrospinal fluid analysis revealed normal counts and protein, with lymphocytes dominating in a smear. Hemogram results are shown.Case 3: Hemogram Test Name Result Empty Cell Reference Interval Units HCT 33 (L) 34–46 % MCV 47 43–55 fL MCHC 35 34–37 g/dL RDW 18.5 16.3–19.3 % WBC 18.0 (H) 5.2–10.1 × 103/μL Segmented neutrophils 9.0 (H) 2.7–6.6 × 103/μL Band neutrophils 0.0 0 × 103/μL Lymphocytes 8.7 (H) 1.2–4.9 × 103/μL Platelets 190 94–232 × 103/μL RBC examination No significant
Case 4
A 2-year-old Quarter Horse gelding presented with progressive lethargy and decreased performance for 1 month. The horse was tachycardic and tachypneic with pale mucosa. Hematologic results are shown.Case 4: Hemogram Test Name Result Empty Cell Reference Interval Units HCT 10 (L) 34–46 % MCV 59 (H) 43–55 fL MCHC 36 34–37 g/dL RDW 27.6 (H) 16.3–19.3 % WBC 4.2 (L) 5.2–10.1 × 103/μL Segmented neutrophils 2.2 (L) 2.7–6.6 × 103/μL Band neutrophils 0.0 0 × 103/μL Lymphocytes 1.8 1.2–4.9 × 103/μL Monocytes 0.1 0–0.6 × 103/μL Platelets 29 (L) 94–232 × 103/μL Mean
Disclosure
The author has no conflicts of interest to disclose.
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