Erythroid Flashcards
List the components of blood
- Fluid (plasma/serum)
- Ions
- Proteins (albumin, globulin, hormones, mediators, clotting factors, nutrients)
- Lipids
- Carbohydrates
- Gas
- Cells
List the functions of blood
- Transport: nutrients, oxygen, waste removal, hormones and other mediators
- Fluid/electrolyte haemostasis
- coagulation
- thermoregulation
What are reticulocytes?
Immature non-nucleated erythrocytes prematurely release to blood from bone marrow in regenerative anaemias. Names based on stain used - DiffQuik = polychromatophils, NMB = reticulocytes
Describe the appearance of reticulocytes
- Romanowsky stains: Polychromatic, blue-pink mixed colour due to staining of ribosomes and haemoglobin
- Using new methylene blue stain: precipitation demonstrates RNA protein complexes
What is the clinical relevance of reticulocytes?
- Evaluation of erythropoiesis in bone marrow
- Differentiation of regenerative and non-regenerative anaemia
What is the absolute reticulocyte count?
The observed percentage of reticulocytes x RBC and is independent of variation of RBC numbers, ggiven as x10^9/l
What are the methods for the assessment of reticulocyte production?
- Reticulocyte count (gives percentage)
- Absolute reticulocyte count
- Reticulocyte production index (sometimes used in dogs, going out of favour)
What are the 2 patterns of reticulocyte staining in cats?
- Aggregate
- Punctate
Describe the dog-specific reticulocyte response (normal vs regerenative anaemia)
- Low number of reticulocyte (<1%) in a healthy animal
- Little regerenation of RBCs needed (live for ~100 days)
- > 60x10^9/l in regenerative anaemia (>10 polychromatic cells per oil immersion field)
Describe the cat specific reticulocyte response (normal vs regenerative anaemia)
- Low numbers normally ().2-1.6%)
- Aggregate = 0.5% of erythrocytes, punctate = 1-10%
- .50x10^9/l in regenerative anaemia
Which type of reticulocyte is considered in cats in the assessment of regeneration?
Aggregate
Compare the appearance of aggregate and punctate reticulocytes
- Aggregate: blue stained, coarse clumping
- Punctate: small, blue stained dots
Describe the ruminant and hose specific reticulocyte response (normal and anaemia)
- Virtually no reticulcytes in normal blood, can regenerate when have anaemia but generally do not release these into blood in normal animal
- Reticulocytes may not appear even in very severe anaemias in horses
- In cattle, peak production 7-14 days post acute blood loss
Compare the platelet size in dogs and cats
Platelet vs RBC size differs more in dog than cat
Outline some haematological variations within dog breeds
- Macrocytosis in some poodles
- Akitas have unusually small erythrocytes and particularly high potassium content
- Greyhounds have high PCVs (0.55-0.6l/L)
What is red blood cell size measured by?
MCV (fL) = mean corpuscular volume = PCV (L/L) x1000/RBC count (10^12/L)
What conditions are indicated by macrocytosis of RBCs?
- Regenerative anaemia
- FeLV infection
- Myeloproliferative disease
- Normal in poodles
What does hypochromic macrocytosis indicate?
Regenerative anaemia haemorrhage, haemolysis)
What does normochromic macrocytosis indicate?
Non-regenerative anaemia, assocaited with FeLV usubgroup A in kittens and myeloproliferative disorders in dogs and cats
What does hypochromic microcytosis indicate?
- With anaemia: classic iron deficinecy, chronic external blood loss
- Without anaemia: portosystemic shunts
What is the most common cause of iron deficiency in dogs?
Occult loss from GIT
Explain how microcytosis occurs as a result of iron deficiency
- At a certain haemoglobin concentration this triggers the cell to stop dividing
- Where this takes longer to reach due to deficiency,t he cell will continue to get smaller until the correct concentration is reached
What conditions may cause microcytosis?
- Iron deficiency
- Altered iron metabolism
- Dogs/cats with portosystemic shunts
- Normal in Akitas
What is Red Cell distribution Width?
A numeric representation of the variability in RBC size, more sensitive than MCV
How is red blood cell colour assessed?
MCH and MCHC (mean cell haemoglobin/concentration in cells)
What is MCHC?
- g/L = Hb (g/L)/PCV (L/L)
What is MCH?
- pg = Hb (g/L)/RBC (10^12/L)
Compare the use of MCHC and MCH
MCHC more useful than MCH since cell size is taken into account
Explain what is meant by normochromic and hypochromic red blood cells
- Normo: normal MCHC, normal Hb content
- Hypo: low MCHC, low Hb content
What may cause a raised MCHC?
- Not physiologically possible
- Almost always due to sample or in vivo haemolysis
- May be artifactual in lipaemic samples
- or Heinz bodies
What is the haemoglobin distribution width?
Hb equivalent of RDW, numeric equivalent to seeing polychromasia on slide
What is indicated by normochromic, microcytic red blood cells?
Most likely analytic error, miscounting paltelets
What is indicated by microcytic, hypochromic cells?
Fe deficiency or PS shunts
What is indicated by macrocytic, hypochromic cells?
Regenerative anaemia (or cell swelling in sample transport)
What is indicated by normocytic, normochromic red blood cells?
If anaemic, often inflammation/chronic illness
Name the different morphological appearances of red blood cells
- Codocytes
- Acanthocytes
- Spherocytes
- Schistocytes
- Burr cells/crenation
Define poikilocytosis
Alterations in cell’s shape, may be due to abnormal erythropoiesis or specific organ dysfunction
describe the appearance of codocytes
- Aka target cells
- Central haemoblobinised area surrounded by an area of pallor, periphery of cell contains band of haemoglobin
- Lack normal biconcave cross section due to folding of cell membrane
What may cause the production of codocytes?
- Iron deficiency anaemia
- Liver disease with cholestasis
- After splenectomy in dogs
What are leptocytes?
Thin, empty RBCs
Describe the appearance of acanthocytes
- Aka spur cells
- Rounded projections of variable diameter and length, unevenly distributed
What causes the formation of acanthocytes?
- Increase in membrane cholesterol or associated with RBC fragmentation
- See in diffuse liver disease
- Splenic haemangioma
- Haemangiosarcoma
- Portosystemic shunts
- High cholesterol diet
Describe the appearance of spherocytes
- Small, densely staining spherical RBCs lacking central pallor
- Small portions of cell membrane may have been phagocytosed by mononuclear phagocytes residual cellular tissue resume that smallest shape possible i.e. sphere
What causes the formation of spherocytes?
- Immune mediated haemolytic anaemia in dogs
- Presence of surface bound antibodies or complement
- Present in animals that have had transfusions
Describe the appearance of schistocytes
Irregular, fragmented erythrocytes due to mechanical trauma to circulating erythrocytes
What causes the formation of schistocytes?
- DIC, other angiopathies
- Immune mediated anaemia
- Thrombosis
- Splenic haemagiosarcoma
- Hypersplenis
- Glomerulonephritis
- Congestive heart failure
- Valvular heart disease
- Doxorubicin toxicosis and myelofibrosis
Describe the appearance of crenation in ertyrhocytes aka burr cells
RBCs with spiked projections of uniform length
- aka echinocytes
What may cause the formation of burr cells?
MOSTLY artifactual e.g sampling into EDTA tube with incorrect ratio blood to EDTA
- Some normal in ruminants
- Rarely snake envenomation
- Occasionally dehydration
Describe rouleaux formation
- Clustering of RBCs in standing blood
- Normal in horses
- Increased stickiness of plasma with increased globulin content
What does rouleaux formation indicate in small animals?
Inflammation
How can rouleauxz formation and agglutination be distinguished from one another?
- To confirm agglutination, mix 1 drop blood with 1 drop saline
- Agglutintion persists due to antibodies sticking RBCs together, rouleaux will disperse
What are the pathological causes of agglutination?
Immune mediated haemolytic anaemia, mismatched blood transfusions (agglutinate due to presence of antibodies sticking cells together)
Describe the appearance of Heinz bodies
Irregular shaped, refractile inclusions consisting of oxidative denatured haemoglobin
What may cause the formation of Heinz bodies?
- Up to 10% of RBCs in normal cats
- Paracetamol and onion toxicity (+ other oxidative compounds)
- Diabetes mellitus
- Lymphoma
- Hyperthyroidism
What stain should be used to confirm the presence of Heinz bodies?
New methylene blue (NMB)
What causes basophilic stippling of RBCs in dogs, cats and ruminants?
- In vivo aggregation of ribosomes into small basophilic granules, caused by low levels of pyrimidine 5’-nucleotidase (P5N) enzyme that catabolises ribosomes
- In cats and dogs: intensely regenerative anaemia, lead poisoning
- Normal in immature erythrocytes in ruminants
Describe the appearance of basophilic stippling
- Multiple, small, dark blue, punctate aggregates in RBCs
What are metarubricytes and what are they also known as?
- Nucleated erythrocytes
- aka nRBCs, normoblasts
What are the potential causes of the formation of metarubricytes?
- Regenerative anaemia
- Production of RBCs outside of the bone
- Non-functioning spleen
- Marrow damage
What causes the formation of nucleated erythrocytes in the absence of polychromasia in cats?
Myelodysplasa or myeloproliferative disease
What is the significance of nucleated RBCs with regards to laboratory analysers?
May count as white cells, need to check manually on slide if these are present
What are Howell-Jolly bodies?
refractile, singlye blueish bodies in RBCs of variable size, representing nuclear remnants
What may cause the formation of Howell-Jolly bodies?
- Regenerative anaemia
- Splenectomy
- Suppressed splenic function
- Higher percentage normally seen in cats
Describe the appearance of babesiosis on blood smears
- Visible intracellular as eosinophilic blobs
- Can cause haemolytic anaemia, systemic inflammatory syndrome, multiple organ dysfunction syndrome
Describe the appearance of Mycoplasma haemofelis on blood smears
Highly pleomorphic, apperaing as chains, discs or rods on surface or embedded into RBC membranes
Briefly outline the clinical signs of Mycoplasma haemofelis (and give the alternative name)
- Haemobartonella felis
- Regenerative anaemia, pyrexia, malaise
What is the rule of 3 and how can errors be identified on haematology?
- Look at MCHC
- HCT% approx = Hb (g/dL) x3 (+/-3%)
- If this is not true for the sample, the something has been mismeasured
- When PCV, RBCC, Hb increase/decrease usually do this in line with each other, if discordant is abnormal, need to find out why = rule of three
What may lead to an incorrect PCV?
- RBCs miscounted e.g. mistaken for platelets
- MCH misleading (cell shrinkage or swelling as consequence of handling or dehydration_
What artefacts commonly occur regarding MCV?
- Swelling of transport
- Mis-identification (pairs, triplets cross over with large platelets)
- Cell shrinkage or expansion in sample e.g. hyperosmolar
How is PCV calculated?
MCV x RBCC
What needs to be considered when evaluating the erythron?
- Is there inadequate, adequate or excessive red cell mass to deliver oxygen to tissues?
- Evidence of anaemia? Regeneration?
- Evidence of polycythaemia? Relative or absolute?
List the main classifications of anaemia
- Normocytic normochromic
- Macrocytic hypochromic
- Microcytic hypochromic
What is polycythaemia?
Increase in PCV, Hb concentration and RBC count
Compare polycythaemia in humans and in dogs and cats
- In humans, usually implies increased number of several haemopoetic cell lines
- In dogs and cats, usually have normal neutrophil and platelet counts with polycythaemia vera
What is meant by relative polycythaemia?
Apparent increase in RBC due to decrease in fluid circulation, also often increased total protein and albumin
What are the causes of relative polycythaemia?
- Dehydration: water or cellular fluid loss e.g. V/D, PU, extensive burns, adipsia, water deprivation
- Splenic contraction due to adrenaline secretion e.g. exercise, fear, excitement, severe pain, stress
What is absolute polycythaemia and name the types
True increase in RBC mass due to increased RBC production/release
- Primary polycythaemia vera
- Secondary polycythaemia
Describe primary polycythaemia vera
- Rare myeloproliferaive disorder, abnormal response of RBC precursors, normal EPO levels
Describe secondary polycythaemia
- Chronic tissue hypoxia of renal tissues due to heart/lung disease
- High altitude
- Thrombosis
- constriction of renal vessels
- Renal tumour or cysts increasing intracapsular pressure preventing inflow of blood
- Increased EPO release by kidneys
What aspects of the erythron are assessed in the investigation of disease of the erythroid system?
- Red cell mass (PCV, RBCC, Hb)
- Evidence for effectie erythropoiesis (size, colour, reticulocyte count)
- Red cell size and variation (MCV, RDW)
- Red cell hemoglobinisation (colour, MCHC)
- Red cell shape and inclusions (smear)
- i.e. size, shape, colour, distribution, structure
What are eccentrocytes?
RBCs with ragged appearance, poorly haemoglobinised fringe of cytoplasm along one side of cell
What causes the formation of eccentrocytes?
- Excess oxidant stress to erythrocytes
- Inherited glucose-6-phosphate deficiency increasing susceptibility to oxidant induced erythrocyte injury e.g. onion poisoning
Give examples of congenital portosystemic shunts
- Persistent sinus venous connection
- Direct portal vein connection
- Connections to caudal vena cava or azygous vein
What causes the formation of acquired portosystemic shunts? Describe the structure
Portal hypertension typically
- Typically multiple extra hepatic shunts that connect the portal system to the caudal vena cava
Which animals are predisposed to congenital portosystemic shunts?
- Yorkies
- Miniature schnauzers
- Irish Wolfhounds
- Old english sheepdogs
- Cairn terriers
- Mixed breed cats
Describe some diagnostic features for portosystemic shunts
- Central nervous system signs
- Poor growth
- Non-specific GI signs
- crytporchidism in dogs and cats
- PUPD in dogs
- Cats: Heart murmurs, seizures, ptyalism, copper iris colour in cats
Compare the types of portosystemic shunts found in small and large breed dogs
- Large: usually intrahepatic
- Small; usually extrahepatic
What would the following signs be indicative of in a dog? Mild non-regenerative anaemia with microcytosis and poikilocytosis Mildly elevated ALT and ALP Low BUN Hypocholesterolaemia Hypoglycaemia Hypoalbuminaemia and globulinaemia Seizures, V/D, PUPD, poor growth
Portosystemic shunt
What is the reticulocyte production index used for?
Corrects reticulocyte count for PCV and indicates if level of regeneration is appropriate
What is CRP?
Corrected reticulocyte percentage
