Red Blood Cells Erythrocytes (RBC’s)

Formed Elements (Cells) of Blood Red blood cells (erythrocytes) White blood cells (leukocytes) Granular leukocytes Agranular leukocytes Platelets (special cell fragments)

Complete Blood Count (CBC) Definition – series of tests performed on whole blood, looking at the 3 types of blood cells White blood count & differential white count (“WBC & Diff”) RBC indices Hemoglobin Packed cell volume (PCV) RBC morphology Platelet evaluation

CBC Equipment

Hemograms A written record of the CBC Includes the following: RBC indices WBC indices Platelet evaluation General Comments on any unusual findings

Erythrocytes

Erythrocyte Terminology Erythrocyte function Erythron Erythrocyte (RBC) Polycythemia Anemia Regenerative Degenerative

Laboratory Tests Used to Evaluate the Erythron Packed Cell Volume (PCV) Hemoglobin (Hg or Hb) RBC Count Mean Corpuscular Values Erythrocyte Sedimentation Rate (ESR)

Packed Cell Volume (PCV) Also known as “Hematocrit” (Hct) Definition – the % of whole blood composed of RBC’s Most frequently used erythrocyte test

Packed Cell Volume (Hematocrit) Centrifuging blood forces formed elements to separate from plasma PCV is % of total volume that is RBC’s

Anatomy of a PCV Tube Clay or wax plug RBC’s Buffy Coat Heaviest specific gravity of cells Sinks to bottom after centrifuge Thickest layer Buffy Coat Thin white layer…….. What is in this layer? Plasma – usually yellow NOT serum…… Why?

Anatomy of a PCV Tube

Hematology Reference Ranges

Normal PCV Values Hematology Reference Ranges (Hendrix) Horse?  Dog = 37-55% [mean = 45] Cat = 30-45% [mean = 37] Horse?  Other RBC Indices in this Appendix A RBC (Red Blood Count) Hemoglobin Mean Corpuscular Values

Influences on PCV Physiological (non-disease) Pathological (disease) High altitude……. Polycythemia Why? Excitement increases PCV [horses especially] Why? Excessive IV fluids decreases PCV [Hemodilution – more plasma] Pathological (disease) Dehydration [Hemoconcentration – less plasma] Anemia decreases PCV (less RBC’s)

Hemoglobin Testing What is hemoglobin? Function of hemoglobin Hemoglobinometer – Refractometer used to obtain hemoglobin concentration Formula for rough estimate of hemoglobin Hb = PCV/3 results in grams per decaliter (g/dl) Average canine hemoglobin = 12-18 g/dl

Use of Refractometer

RBC Count Use of hemocytometer Use of electronic cell counters Technique the same as for WBC Count, except dilution factors and counting areas As much as a 20% error!!! Use of electronic cell counters More accurate than hemocytometers Formula for rough estimate of RBC Count RBC Count = PCV/6 results in millions per microliter

Erythrocyte Indices Also known as Mean Corpuscular Values Definition – A look at the average (mean) RBC size, hemoglobin, and hemoglobin concentration Calculated by referral labs and reported on lab reports sent to veterinary hospital Used by DVM to help in diagnosing type of anemia present

3 Erythrocyte Indices Mean Corpuscular Volume (MCV) SIZE of the average RBC Helpful in determining what type of anemia might be present Mean Corpuscular Hemoglobin (MCH) Average WEIGHT of hemoglobin in the average RBC Not very helpful Mean Corpuscular Hemoglobin Concentration (MCHC) Average CONCENTRATION of hemoglobin in the average RBC

Erythrocyte Sedimentation Rate (ESR) Measures rate at which RBC’s separate from their plasma in a column of whole blood (that has anticoagulant) How fast RBC’s fall in a vertical tube over a given period of time Wintrobe Hematocrit Tube Used for prognosis, not diagnosis Not used too often in veterinary medicine

Interpretation of ESR Horses – RBC’s tend to stack up in a “stacked coin” arrangement (Rouleaux Formation) Increased ESR Anemia – little traffic in the Tube Increased PCV – bumper to bumper traffic in rush hour Decreased ESR

Erythrocyte Morphology Normal Morphology Size abnormalities Shape abnormalities Color abnormalities RBC Inclusions

Normal Erythrocyte Morphology Most common of blood cells on a blood smear Biconcave disc No nuclei in mammal RBC’s Nuclei present normally in bird and reptile blood Normal canine RBC’s have a central pallor (lightness) to them

Erythrocytes on a Needle

RBC Size & Pigment Normocytic Macrocytic Microcytic Normochromic Hypochromic No such thing as “Hyperchromic” Why?

Erythrocyte Size Abnormalities Record abnormal findings under “General Comments” on the hemogram Anisocytosis Macrocytes Microcytes Normocytic

Erythrocyte Shape Abnormalities (Poikilocytosis) Schistocytes Acanthocytes Crenation (Echinocytes) Keratocytes Spherocytes Target Cells (Codocytes)

Erythrocyte Shape Abnormalities Poikilocytosis – general term for shape abnormalities

Schistocytes RBC fragments

Acanthocytes (Spur cells) Unevenly distributed surface projections of different lengths

Crenation Echinocytes (Burr cells) – spiculated (pointed) cells with short, evenly spaced surface projections Artifact? – slow drying of blood films Feline blood

Crenation (Echinocytes)

Keratocytes Helmet cells – contain a vacuole?

Spherocytes Darkly staining RBC’s with no central pallor Canine only? Autoimmune hemolytic anemia

Target Cells (Codocytes) RBCs with central rounded area of hemoglobin surrounded by clear zone A few in normal blood? Associated with anemias

Target Cells

Erythrocyte Color Abnormalities Normochromic Polychromasia – polychromatophilic RBCs Blue tint to cytoplasm, due to presence of organelles remaining in cytoplasm (young cells) Hypochromic – decreased staining due to insufficient hemoglobin in cells Hyperchromic (no such thing!)

Nucleated RBCs (NRBCs) RBC Inclusions Reticulocytes Basophilic Stippling Howell-Jolly Bodies Heinz Bodies Nucleated RBCs (NRBCs)

Reticulocytes Immature RBCs that contain organelles (ribosomes) As cell matures they are lost Account for diffuse blue-gray stain with Wright’s stain 1% in normal circulation Special stains needed usually

Basophilic Stippling Presence of small, dark-blue bodies all over RBC Represents residual RNA Common in immature RBCs

Howell-Jolly Bodies Basophilic nuclear remnants Seen in young RBCs in response to anemia Phagocytes in spleen remove these remnants

Heinz Bodies Rounded structures representing denatured hemoglobin Pale or blue area, depending on stain Cause: certain oxidants or drugs Normal cats may have them

Heinz Bodies

Nucleated RBCs (NRBCs) Also called metarubricytes Represent early release of immature cells during anemia If > than 5 per 100 WBC’s Correct WBC Count Normal in bird & reptile blood

NRBC’s – How Many Do You See?