Haematology is the study
of blood disease and diseases of the blood forming organs.
Many people say that haematology is more of an art than a
science and this is particularly appropriate when one
considers the morphological assessment of red cells, white
cells
and
platelets which is a critical part of a haematological
assessment. Although cell numbers are obviously important, a
complete cell count (CBC)
or full blood count (FBC) on its own is simply not enough . At
CTDS every haematology
submission has an automated cell count performed and also has
a white cell differential and cell morphology examination made
on on a prepared blood film. All blood smears are examined in
the first instance by a qualified haematologist and then, if
certain criteria are met, also by a veterinary
pathologist.
For routine haematology we recommend the
submission of whole blood taken into EDTA anticoagulant (or
Lithium heparin for exotics or small samples that also require
biochemistry) and a freshly prepared blood film made at the
time of phlebotomy. The cell morphology of a freshly prepared
smear is generally superior to that of a sample taken and
stored in EDTA and assists our evaluation greatly (glass
microscopy slides and slide holders are available from CTDS on
request).
For coagulation profiles, PT and or APTT submissions
please submit a sample taken into sodium citrate also.
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Quality samples for
haematology
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It is especially important
for haematology that the blood sample is not clotted -the
presence of fibrin clots in haematology samples give results
that are erroneous. At CTDS we check every sample for the
presence of fibrin clots before analysis and examine the smear
for evidence of platelet clumping.
Anticoagulants in haematology
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Anticoagulant
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Tube Top Colour
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Test required
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EDTA Whole Blood (1ml)
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or
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FBC, CBC, Coagulation profile, all
screens and profiles.
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Citrate (1ml)
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!
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or
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PT, APTT and Coagulation profile
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Lithium Heparin whole blood (1ml)
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or
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!
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Avian and reptilian haematology -also
GshPX and Lead
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! check label - green
tops maybe heparin or citrate (coagulation)
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Good sampling techniques:
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Wherever possible, sample from larger vessels e.g. jugular
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Immediately transfer blood from the syringe into
anticoagulated tubes first ensuring the tip of the syringe
does not touch
the side of the tube (fill serum tubes
last)
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As soon as blood is transferred into the anticoagulated tube,
mix the sample by gentle inversion 20 times, or by
rolling
the tube on a flat surface for 30 seconds
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Ensure anticoagulant tubes (particularly EDTA) are filled to
the recommended level and do not overfill
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Ensure all tubes containing anticoagulant are within the
expiry date shown on the tube label
N.B. Citrate tubes have a very short shelf life – order just
before use. Citrate tubes should be stored in the refrigerator
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Blood smear preparation
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Using either fresh EDTA whole blood or a drop of fresh blood
from the tip of a syringe:
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Place a small drop of blood onto a clean, grease free glass
slide.
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Take another clean glass slide as a spreader, preferably one
with a bevelled edge, and draw this back into the blood drop
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Allowing the blood to flow across the spreader surface
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Holding the spreader at an angle of approximately 30 degrees,
move the spreader "gently" forward in a single
smooth action
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Spread to the end of the slide - do not lift the spreader
from the slide
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Label the smear and allow to air dry (do not heat)
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All fresh blood films are invaluable but a "perfect"
blood smear should have a smooth rounded tail, approximately
one cell thick at its tail, and cover approximately 2/3rds of
the length of the slide
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The cells should be distributed evenly in a layer one cell
thick over the tail of the smear
Common problems
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If the blood film "falls off" the end of the slide
try either using less blood and/or moving the spreader faster
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If the blood film is too short or too thin, try using a
little more blood and/or spreading more slowly
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The prescence of "smudged" white cells, although
occasionally clinically significant, is often associated with
"hard" spreading
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Red cells that overlap at the tail - too much blood and or
spread too slowly
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Absence of white cells in the body and many white cells at
the tail - spread too slowly or lifting the spreader before
smear completion N.B. it is normal to have more white cells
at the tail but an absence of white cells in the body is not
normal
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Common haematology terms and abnormalities
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Anisocytosis
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Anisocytosis means that the red cells
are of unequal size. It is a feature of many anaemias, and
other blood conditions, and does not have much diagnostic
value. The 'red cell distribution width' (RDW) is a
quantitative measure of the degree of anisocytosis. The
RDW is useful in the differential diagnosis of microcytic
anaemia
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Acanthocytes
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Acanthocytes (also known as "spur
cells") may be described as red cells with
finger-like projections - typically 5-10 irregular, blunt
projections (which vary in width, length and surface
distribution and should not be confused with echinocytes).
These cells have a decreased survival time and may be
observed in liver disorders, increased blood cholesterol
content or from the presence of abnormal plasma
lipoprotein composition .
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Dohle bodies
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Dohle bodies appear as single or
multiple light blue or grey staining areas in the
cytoplasm of a neutrophil. They are rough endoplasmic
reticulum containing ribonucleic acid (RNA) and may
represent localised failure of the cytoplasm to mature.
Dohle bodies are found in infections, poisoning, burns,
and following chemotherapy.
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Echinocytes
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Echinocytes (also called "crenated
cells") are morphologically altered red blood cells
that appear to have numerous, fine, uniform spicules
throughout the cell membrane. Echinocytes are often
overlooked as an artifact of preparation e.g. due to
storage or slow drying bloodsmears, however several
disease processes (e.g. lymphosarcoma (partially as a
result of chemotherapy), pk deficiency, uremia) and toxins
have been found to alter the red blood cell membrane which
leads to the formation of echinocytes.
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Haemobartonellosis
Feline
infectious anaemia (FIA) also known as Mycoplasma
felis
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The most common red cell parasite in
the UK is Haemobartonella felis which is a gram
negative epicellular parasite found in feline
erythrocytes. Red blood cell destruction is due primarily
to immune-mediated events and direct injury to red blood
cells induced by the organism is minimal. The attachment
of the organism to erythrocytes commonly leads to the
development of antibodies against the organism as well as
to erythrocyte antigens so positive Coomb's tests are
common. Clinically haemobartonellosis and primary immune
haemolytic anaemia are difficult to differentiate. For the
diagnosis of both these conditions an EDTA sample and
fresh air dried blood film are required.
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Howell Jolly Bodies
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Howell-Jolly bodies are round, purple
staining nuclear fragments of DNA in the red blood cell.
They are usually observed singly in haemolytic anaemia,
following splenectomy, and in cases of splenic atrophy.
Multiple Howell-Jolly bodies may be observed in cases of
megaloblastic anaemia.
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Macrocytes
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Macrocytes are red cells with an
increased size, 9-12µm in diameter. They may be found in
liver disease and megaloblastic anaemia, when associated
with vitamin B12 or folic acid deficiency, the macrocytes
may appear slightly oval in shape.
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Normochromic
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Normochromic describes the red cells as
being of normal colour i.e. indication of haemoglobin
content, for the species
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Normocytic
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Normocytic describes the red cells as
being of normal size i.e. diameter for the species.
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Poikilocytosis
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Poikilocytosis is a term which
indicates that red cells of abnormal shape are present on
the blood film. Of itself it is fairly non-specific. Some
particular types of poikilocyte are very informative,
however. The 'tear-drop' poikilocyte is a characteristic
feature of marrow fibrosis, but it can also be seen in
other conditions.
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Schistocytes
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Schistocytes are red blood cell
fragments that result from membrane damage encountered
during passage through vessels. They occur in
microangiopathic haemolytic anaemia, severe burns, uremia,
and haemolytic anemias cause by physical agents, as in
disseminated intravascular coagulation (DIC). They are
sometimes referred to as "bite cells".
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Spherocytes
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Spherocytes are red cells which are
almost spherical in shape. They are not biconcave like a
normal red blood cell and do not have the central area of
pallor which a normal red cell shows. These cells are
associated with haemolytic anaemia
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For
Veterinary Haematology Images - click here
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?
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Seen a veterinary haematology phrase or term and unsure of
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