Clinical Haematology 3

Question 1

Bone marrow production.

Answer 1

Pluripotent stem cells.
Lymphoid stem cells come off lymphoid stem cells and set up centres outside bone marrow (to lymphoblasts to B cells (memory cells, plasma cells, antibodies) and T cells (to NK cells).
Myeloid stem cells come off pluripotent stem cells and go on to form megakaryoblasts (to megakaryocytes to platelets), erythroblasts (to form reticulocytes to erythrocytes), monoblasts (to monocytes to macrophages), myeloblasts (to granulocytes – basophils, eosinophils, neutrophils).

Question 2

How do we assess WBCs in labs?

Answer 2

Haematology analysers and blood film examination.

Question 3

What can we assess with blood film examination?

Answer 3

Morphology and total WBC count and differential estimation (x40 lens).

Question 4

1. How do you carry out a total WBC count?
2. How do you carry out differential estimation?

Answer 4

1. Count all WBC in 10 fields of the blood smear and calculate the mean of each field.
   The mean x1.5 = total WBC count (x10 to power of 9/L).
2. Ideally count 100 cells per 10x10 to power of 9/L WBC count.
   Convert percentage to absolute numbers.

Question 5

1. Where are the neutrophils ‘pools’ in the body?
2. What pool do our sampled neutrophils come from?
3. How long is half-life of neutrophils in circulation?
4. Neutrophil survival in tissues?
   – Where in the tissues do neutrophils accumulate and when may neutrophils be reduced?

Answer 5

1. Bone marrow, ‘birthed’ into blood circulate or marginate, goes into tissues.
2. Circulating pool.
3. 6-12 hours (replaced multiple times a day, even in health).
4. Up to a few days.
   – Sites of inflammation (infectious or sterile). And they may be reduced in disease states.

Question 6

1. What is neutrophilia?
2. What may cause neutrophilia?

Answer 6

1. Increased circulating neutrophils.
2. • Increased production independent of demand due to neoplastic proliferation (rare).
     - Redistribution due to stress or a steroid response, hyperadrenocorticism.
     - Increased persistence in circulation due to stress or steroid response (change in morphology may also be seen).
     - Increased production due to increased demand – infection (bac, other), sterile inflammation (esp. immune-mediated (e.g. IMHA), pancreatitis), neoplasia, tissue necrosis.

Question 7

1. What cells can be seen where there is an increased neutrophil production due to increased demand?
2. What is seen with regenerative left shift?
3. What is seen with degenerative left shift?

Answer 7

1. Immature neutrophils – bands cells (left shift).
2. left shift with neutrophilia.
3. left shift with normal or reduces neutrophil count (more band cells than mature neutrophils = bad sign).

Question 8

1. Why may toxic change in neutrophils occur?
2. What bone marrow changes occur?

Answer 8

1. Neutrophil production under overwhelming demand causing reduced maturation and enhanced neutrophil turnover and changes in the bone marrow.
2. Cytoplasmic basophilia – retained residual
   cytoplasmic RNA.
   Dohle bodies.
   Cytoplasmic vacuolation.
   Toxic granulation – persistence of primary granules.
   Giant neutrophils.
   Ring nuclei.

Question 9

1. What would we expect the cause to be of mild (to moderate) count and normal morphology?
2. What would we expect the cause to be of (mild to) moderate to severe count +/- left shift?

Answer 9

1. Normal physiologic stress.
   Steroids – exogenous or endogenous –> neutrophils may be hyper-segmented. Often accompanied by monocytosis, lymphopenia and other steroid effects.
2. Is there a suspicion of an inflammatory response?
   - Concurrent pyrexia / localising clinical signs.
   - Other leukogram changes consistent w/ increased demand?
   - Serum biochemistry changes: Is this an acute phase protein response?
   – Reduced albumin / increased globulins.
   – Specific biomarkers: C-RP (dogs), fibrinogen / SAA (horses), A1-AGP (cats).

Question 10

1. What is neutropenia?
2. What are the causes of neutropenia?

Answer 10

1. Reduced levels of circulating neutrophils.
2. • Overwhelming demand due to severe inflammatory (often infectious) process.
     +/- degenerative left shift.
     - Decreased production due to bone marrow disease caused by:
     – infectious disease (FeLV, parvovirus, leishmania, ehrlichiosis).
     – Toxins / drugs: oestrogens, chemotherapeutics, bracken fern poisoning (horses), chloramphenicol, (phenobarbital, thiamazole).
     – Myelophthisis (e.g. haemopoietic tissue replaced with fat, fibrosis or neoplasia).
     – Hypoadrenocorticism.
     – Cyclic neutropenia (breed-related).
     - Artefact e.g. sampling error like clot in tube, or agglutination.
     - Anomaly – breed-associated / individual.
     - Destruction e.g. immune-mediated.