But for the rest of this lecture, I want to focus on
the range of investigations that are used for
studying the blood system
and how those are interpreted both in the laboratory
and by the clinical teams.
The first and most important investigation in
haematology is the blood count.
The blood is taken from the patient and
analyzed on a machine.
This is the typical profile that you'll get back from
your patient, obviously giving their details
and a range of values there, different cell types and
values along the bottom.
Let's go through some of these, talk about the normal
values and how we might interpret
some of those abnormalities.
I want to focus particularly on 3 main components within
the blood count:(1)the red cell count and the haemoglobin,
they go very much together, (2)the total and individual
white cell counts and (3)the platelet count
All of that information will be contained within the
blood count and really we have to thank alternative
blood counters for the position we're in in haematology.
The whole discipline was transformed when counters
such as the Coulter counter were invented and these can
count the characteristics of many millions of cells
very very quickly and provide us with
You can see that our machine only got to 16-1/2,
but these automated blood counters have really
transformed our understanding of blood disorders.
Now I'll show you some examples of how that's done.
The normal red cell count in health is around
between 4-6 x 10^12 cells per liter.
That is an awful lot of cells.
We have around 5 liters of blood, so you can
certainly get an idea of the vast numbers of
red cells within your circulation.
The haemoglobin is expressed in grams per liter
and you will see there, the normal range for men,
between 135-175 and for women, around 115-155.
But I want to make a couple of points here.
One is there is a slight difference in different
laboratories as to what the exact normal range is
and it varies slightly with age.
The other thing is, it's quite surprising to have
the value that differs in relation to gender.
The men are slightly higher in this case than women.
If we measured sodium or potassium,
we won't see a difference there.
So why is that? The reason is that the male hormones
are anabolic and they stimulate erythropoiesis and
lead to a slight increase in the haemoglobin
concentration as males pass through puberty.
Now oddly enough, the size of a red cell has become
very important within haematology and this is because
these automated red cell counters the dimension can
provide information on the volume of the red cells
and that's called mean cell volume or the MCV.
That's calculated by just counting the number of cells
in a certain volume of blood and dividing it.
It is a very odd measurement.
You wouldn't know the volume of a liver cell or a
neuron, but in haematology,
we've come to make this very important in our
practice and now let me explain why.
Because as you'll see, the size of a red cell
is a very useful clue in determining
the cause of diseases particularly anaemia.
The volume of a red cell is in this measurement
called femtolitres (fl) and normally it's around 80-95.
If the red cells are small, less than 80,
we call it MICROCYTIC. If it's large,
over 95 and that is one reasonable cutoff,
we call it MACROCYTIC; and that's very characteristic
of different types of anaemia.
White cells are slightly larger cells.
Their normal range is much lower than the red cell,
around 4-7x10^9 per litre, they are thousand
times less common than red cells.
A decrease in white cells, we call that a
LEUCOPENIA; and an increase, LEUCOCYTOSIS.
There are two major types of white cells within
the blood: lymphocytes and neutrophils
and we can use those same terms attached
to -penia and -cytosis.
Let me explain, you could get a lymphopenia and
neutropenia, or lymphocytosis
or actually it is not neutrocytosis, we call it
neutrophilia and I don't know why
that slight aberration has derived
over the last few years.
PLATELETS. If a patient is complaining of bleeding or
bruising, it is important to assess
the platelet count and the platelet function.
We normally have around 150-400x10^9 per litre
platelets within our blood. If it's low,
we call it a THROMBOCYTOPENIA and that can
be because the patient is not producing
enough platelets or there's increased destruction.
If the platelet count is increased, we call that
a THROMBOCYTOSIS and that can increase
the risk of blood clots rather than bleeding.
Now, haematologists and laboratory scientists love to
make blood films and you will see one of the left there.
A little drop of blood is pat on a slide and then
smeared out, left to dry and stained.
That means it can then be looked at under the
microscope and you will see on the right a really
very beautiful, i think blood film and you will see
all the 3 main types of cells on that blood film,
the numerous red cells with its pale centers.
The white cells, in fact, there are two neutrophils
at the top and a lymphocyte at the bottom and at the
back you will see occasional small purple cells,
those are the platelets. You can see straight away
why the blood film is such a critical investigation
for many patients with blood diseases.
We often want to assess blood clotting.
To do this, blood is taken into a tube with an
anticoagulant such as citrate or EDTA
and that means the blood doesn't clot, but what we
can then do is add constituents that make the blood
clot and time how long it takes for that clotting to occur.
There are two major types of blood clotting tests.
One is called the activated partial thromboplastin time
or the APTT, and the other is the prothrombin time
or the PT and these are tests of two slightly different
systems within the clotting cascade.
Sometimes looking at the blood within the vascular
system is not enough, we need to go to where
the blood is made and examine the bone marrow.
Blood is made within the bone marrow and we can
examine the bone marrow by getting access
usually to the bone marrow in the pelvis.
The pelvis is very rich in haemopoietic cell production
and there are two types of examination that we can do.
We can do an aspirate. This is where we will
put a needle into the pelvis
and suck out some liquid bone marrow
and look at it under a slide.
We can also take a trephine, that is a
It is a core biopsy that goes into formalin and
is sliced up and looked at under the microscope.
They're very different pieces of information as we
shall see in a minute.
On the right you will see the areas where we go to
take bone marrow - at the back of the pelvis,
the posterior iliac crest and that is where the
needle is introduced.
Here we have got examples of a bone marrow aspirate
and a bone marrow trephine.
On the left, you will see the bone marrow aspirate.
At first sight, it looks similar to a blood smear
but that is actually bone marrow that has been taken out
of the pelvis and then drawn along the slide
and if you look next to it, that is what an aspirate
looks like when it's stained.
You will see those large areas of fat within the bone
marrow and so an aspirate gives you a very nice
ability to look at the detail of the cells within the
bone marrow, but it completely disrupts the architecture
Whereas the trephine on the right is a
histological specimen, the cells remain untouched
in their natural anatomical distribution.
You can see the bone at the top, then you can see
that perhaps over 50% of this bone marrow is fat
space and then within that you will see haemopoiesis.
The trephine is a critical test for assessing
the cellularity of the bone marrow,
has it got the normal number of cells or are they
reduced or increased?
So we usually do both of these tests when a
patient needs a bone marrow examination.
Now increasingly genetic analysis is entering haematology
as a very important investigation for many patients.
Leukemia derives from malignant white cells and all
haematological malignancies are called cancers of course
developed when there is damaged DNA within a cell,
and genetic analysis is crucial in the diagnosis
and management of many types of cancer now.
There are two major types of genetic analysis
you may wish to do. The first is called a karyotype
and thats where you look at all the chromosomes
within an individual cell.
You remember that we have 23 pairs of chromosomes.
On the right is a really very beautiful example of a
karyotype and the chromosomes have been paired
together and given an individual colour.
In fact on that slide, you may have noticed some
of those who are very eagle-eyed will spot it as what
we call the translocation where part of the
genetic material from one chromosome has
moved to another chromosome.
You'll see it particularly chromosome 16 there.
They are blue chromosomes with slightly different
colour at the top and that has come from
chromosome 8. That is an example of leukemia.
But as well as karyotype, more and more these days,
we have the ability to look for specific genetic
mutations and that involves sequencing genes within
the tumor cells to see where the damage has arisen.
Our cells all have 30,000 different genes, that's
what we inherited from our mom and dad
but the mutational analysis is so sophisticated
that now we have the capacity to sequence
all of those genes and compare a tumor cell to a
normal cell and that will be particularly important
in the new management of malignant diseases.