Leucocyte and platelet abnormalities

What are the major leucocytes in circulations

• Neutrophils

• Monocytes

• Lymphocytes

• Eosinophils

• Basophils

What is WBC count provided by

An automated haematology analyser

What is differential WBC count

Percentages of different leucocyte types

What is the gold standard for differential WBC count

Manual

What is the automated haematology analyser actually counting

Total nucleated cells count rather than total WBC count

How do you do a manual differential WBC count

1. Count 100 WBC at 40x or 100x moving with battlement pattern

2. Classify

3. Calculate absolute numbers by multiplying percentage with total WBC count

What do neutrophils look like

What do lymphocytes look like

What do monocytes look like

What do dog and cat eosinophils look like

What do horse eosinophils look like

What do cow eosinophils look like

What do dog and cat basophils look like

What do horse basophils look like

What do cow basophils look like

How do WBC size compare

Lymphocytes < granulocytes < monocytes

Which WBC have lobed nucleus

• Neutrophils

• Eosinophils

• Basophils

Which WBC have cytoplasmic granules

• Eosinophils

• Basophils

Where are leucocytes produced

• In the bone marrow

• In lymphoid tissues

What are the two leucocyte pools in blood

• Circulating - freely flowing cells

• Marginated - transiently attached to the endothelium

What is the left shift

The hallmark of acute and active inflammation

What are the stages of the left shift

1. Great demand

2. Storage neutrophil pool diminishes

3. Release of immature neutrophils from maturing neutrophil pool

What are band neutrophils

• U or S shaped non segmented nucleus

• Immature

• One stage before segmented neutrophil

What are toxic changes to neutrophils

• Foamy cytoplasm

• Diffuse cytoplasmic basophilia

• Dohle bodies

• Asynchronous nuclear maturation

• Giant neutrophils

• Toxic granules

• Maturation defects occurring during accelerated neutropoiesis

How is neutrophilia caused by inflammation

• Infection, immune-mediated disease, neoplasia, necrosis

• Toxic changes may be seen

• Left shift

How is neutrophilia caused by excess of glucocorticoids

• Endogenous or exogenous glucocorticoids

• Neutrophils up to 2-4x the normal amount

• Less pronounced in cats

• Lyphopenia, monocytosis, eosinopenia

How is neutrophilia caused by excess of catecholamines

• Fear, excitement, exercise

• Transient

• Up to x2 for dogs or x4 for cats

• Lymphocytosis, monocytosis

What are other causes of neutrophilia

• Chronic myeloid leukaemia

• Paraneoplastic syndrome

How is neutropenia caused by increased use

1. Overwhelming acute inflammation

2. Migration of neutrophils to tissue exceeds the release from bone marrow

3. Left shift is typically present

4. Toxic changes may be present

How is neutropenia caused by ineffective production

• Bone marrow disorder

• Infections

• Toxic insult

• Myelofibrosis, myelophthisis

What are other causes of neutropenia

• Endotoxaemia

• Immune mediated neutropenia

• Haemophagocytic syndrome

• Cyclic haematopoiesis of grey collies and FeLV infected cats

How is lymphocytosis caused by chronic inflammation and antigenic stimulation

• Mild to occasionally moderate

• Reactive lymphocytes, neutrophilia, monocytosis, eosinophilia

How is lymphocytosis caused by excess catecholamines

• Fear, excitement, exercise

• Transient

• Up to x2 in dogs or x4 in cats

• Lymphocytosis, monocytosis

How is lymphocytosis caused by lymphoproliferative disease

• Leukaemia and leukaemic phase of lymphoma

• Mild to extreme lymphocytosis

How is lymphocytosis caused by hypoadrenocorticism

Reverse stress leukogram

How is lymphopenia caused by excess of glucocorticoids

• Endogenous or exogenous glucocorticoids

• Most frequent cause

How is lymphopenia caused by acute inflammation

• Stress

• Viral infections

How is lymphopenia caused by depletion

• Loss of lymphocyte rich fluid

• Enteric disease

• Repeated drainage of chylothorax

How is lymphopenia caused by hypoplasia, destruction and disruption of lymphoid tissue

• Multicentric lymphoma

• Immunosuppressive drugs

What are causes of monocytosis

• Inflammation - acute or chronic

• Excess of glucocorticoids

• Other - secondary to neutropenia, chronic myeloid leukaemia

How is eosinophilia caused by hypersensitivity reactions

• Flea bite dermatitis

• Feline asthma

• Food allergy

How is eosinophilia caused by parasitism

• Ectoparasites

• Endoparasites

How is eosinophilia caused by inflammation

• Idiopathic conditions

• Eosinophilic enteritis

• Eosinophilic bronchopneumonia

• Eosinophilic panosteitis

What are other causes of eosinophilia

• Hypoadrenocorticism

• CHronic eosinophilic leukaemia or paraneoplastic

• Hypereosinophilic syndrome

What are causes of basohilia

• Hypersentitivity reactions

• Parasitism

• Neoplasia

What causes monocytopenia

• Healthy animals can have only rare monocytes

• Not a diagnostic problem

What causes eosinopenia

• Stress leukogram

• Healthy animals can have only rare eosinophils

What is haematopoietic neoplasia

Clonal proliferation of lymphocytes or other leucocytes and their precursors

What is haematopoietic neoplasia typically associated with

Marked leucocytosis but reduced numbers of other leucocytes

What characterises acute leukaemia or the leukaemia phase of lymphoma

Poorly differentiated, overtly abnormal cells

What characterises chronic leukaemia or the leukaemia phase of lymphoma

Well differentiated cells

What are platelets

Anucleate cytoplasmic fragments

What is the cytoplasmic appearance of platelets

Pale blue/pink cytoplasm containing clusters of purple granules

What is the origin of platelets

Megakaryocyte in bone marrow

What are thrombocytes in non-mammalian species

True cells

What is platelet count obtained by

The haematology analyser

What is the estimation of platelets in a blood smear

• 1 PLT/OIF = 15 × 10⁹ /L

• 10 platelets in 100x oil objective in dogs cats and bovine

• 5 platelets in 100x oil objective in horses

What causes platelet clumping

• In vitro aggregation

• Slow or poor venepuncture technique

• Delayed or inadequate mixing of blood with anticoagulant

What is thrombocytopenia

Decreased platelet count

When does spontaneous bleeding typically occur in thrombocytopenia

When PLT count <20-30 × 10⁹ /L

What is pseudothrombocytopenia

Falsely low platelet count due to platelet clumping

What should always be done if platelet count is low

Check a blood smear for platelet clumping

Which breeds have breed-specific normal platelet variations

• Sighthounds

• Cavalier King Charles Spaniel

• Norfolk terriers

• Cairn terriers

How is thrombocytopenia caused by sequestration and redistribution

• Splenomegaly, sever hypothermia, endotoxaemia

• Mild to occasionally moderate in severity

How is thrombocytopenia caused by increased consumption

• DIC, thrombosis, vascular neoplasm, vasculitis, massive acute blood loss

• Large platelets may be seen

How is thrombocytopenia caused by increased destruction

• Autoimmune, infectious agents, drugs, neoplasia

• Large platelets may be seen

How is thrombocytopenia caused by inadequate production

• Decreased or ineffective production

• Idiopathic, infectious agents, drugs, toxins, myelophthisis, myelodysplasia

What are the clinical signs of thrombocytopenia

• Petechiae - haemorrhages in skin

• Ecchymosis - mucosal haemorrhage

• Epistaxis - nose bleeds

• Melaena - digested blood if faeces

• Maematochezia - blood in faeces

• Haematuria - blood in urine

What is thrombocytosis

• Increased platelet count

• Usually no clinical significance unless extreme

What are the causes of thrombocytosis

• Splenic contraction

• Inflammation

• Neoplasia

• Iron deficiency anaemia

• Post splenectomy

• Hypercortisolaemia

• Drugs

What are large/giant platelets

Platelets seen on a blood smear or identified by increased MPV

When is a platelet considered giant

If it is bigger than a RBC

In which species are large platelets common in healthy individuals

Cats

What do large/giant platelets suggest

Accelerated and active thrombopoiesis

What is inherited macrothrombocytopenia

• A breed specific normal variation

• Not associated with bleeding diathesis

• Common in cavelier king charles spanial, norfolk terrier and cairn terriers