I’m just going to describe a little bit
about how we might use these tests in real
So, for example, we have a patient who presents
in outpatients with breathlessness. They’ve
been breathless for a few weeks on exertion.
The question is: what’s the disease that’s
causing it? Well, firstly, we do a full blood
count. Are they anaemic? We must make sure
they’re not anaemic as that’s a good cause
of dyspnoea and is easy to discount by a full
blood count. If they have a lung disease causing
breathlessness, then their physiology will
be abnormal. So we do a spirometry, lung volumes
and we do a transfer factor as well. And that
will fully evaluate whether the lungs might
be contributing towards their dyspnoea.
A chest x-ray is also done because, if they
have any pleural interstitial lung diseases,
they should have an abnormal chest x-ray.
For airways diseases such as asthma and COPD,
the x-ray will look fairly normal but, if
they have any infiltration in the lung due
to interstitial lung disease such as pulmonary
fibrosis, it should be visible on a chest
And the last thing we need to think about
is: could this be a cardiac problem? And we
might want to do echocardiograms, an ECG,
a measurement of the brain natriuretic peptide
level in the blood, all of which will identify
patients who have cardiac-valve problems or
cardiac failure, issues which might be making
And when we get the results of those tests,
it might dictate what we do next.
So, for example, if you have somebody with
abnormal lung function and it shows an obstructive
spirometry, then that suggests they could
have asthma or COPD. And that might be an
adequate enough investigation to identify
what the problem might be.
If it’s restrictive spirometry, then you
have to think about interstitial lung disease
or chest-wall problems as the cause of their
breathlessness. And that may require further
If they have a fall in their transfer factor,
then that’s actually a very important observation
because there are only really two or three
major causes for that. One is emphysema but
they should have obstructive lung function
with that as well. Two is interstitial lung
disease. And the third would be pulmonary
emboli or pulmonary hypertension. So pulmonary
vascular disease of some description.
If the x-ray is abnormal, then you really
need to get more information about what that
abnormality might be due to. If it’s breathlessness
that’s the problem, then we’re thinking
about pleural disease which will require an
ultrasound or a CT scan to assess in more
detail. If it shows interstitial lung disease,
then a CT scan is absolutely necessary to
identify what’s going on in more detail.
So this will lead onto our next set of investigations,
obstructive spirometry: is it reversible or
irreversible obstruction? And that will dictate
whether the patient has asthma or COPD to
a certain extent. If it’s restrictive spirometry,
you need a CT scan to assess the lung parenchyma
in more detail. The same if you suspect potential
interstitial lung disease because of the chest
x-ray changes. And if there’s a low transfer
factor, you do need that CT scan to look for
interstitial lung disease but also you might
need to think about the pulmonary vessels
and do a CT pulmonary angiogram to assess
those in more detail and potentially do an
echocardiogram to make sure they don’t have
Now, that’s somebody presenting with dyspnoea
– shortness of breath – in outpatients.
If you have somebody who’s got lung cancer,
it’s actually a very different scenario
and a very different set of tests become important.
So somebody presents: mass on the chest x-ray,
they’ve coughed a bit of blood or something
along those lines, they make you suspect they
may have lung cancer. Actually they’ve had
their chest x-ray. The next test is – there’s
a mass, we need to define that in more detail.
Let’s do a CT scan to get a three-dimensional
vision of that mass to see exactly where it
is in the lung, what tissues it might adjoining
to. And in addition, we may want to stage
the patient to see whether they have liver
or adrenal involvement, metastases perhaps
from that original lung cancer.
We do some blood tests. And the reason why
we do those is that, again, that actually
helps identify patients who may have metastases
because the alkaline phosphatase will be raised
with bone metastases and with liver metastases.
And we need to know about calcium, U&Es because
there are complications of cancer that might
affect those electrolytes.
And then actually the most important test
will be a biopsy. So once you’ve done the
CT scan, the next question is: which biopsy
modality you will use? That would be dictated
by the anatomy that you have defined using
the CT scan. And you’ll do a biopsy and
get the histological results and that will
then dictate the treatment. And further tests
might be required to see whether that treatment
So, for example, if somebody has got a lung
mass, it turns out to be a cancer, it turns
out to be a localised cancer but they have
background COPD making them short of breath
on exertion. We may want to resect that cancer
but the worry here is that that’ll make
them more breathless because, to resect the
cancer, we’re going to have to remove a
large amount of lung. So you measure their
lung function and get a feel for whether they
could cope with that lung resection without
ending up in respiratory failure.
And so on. We might do tests regarding kidney
function to make sure they can cope with the
So to summarise this lecture:
Diagnostic tests have to be used in a targeted
way to answer specific clinical questions
when you’re assessing the patient. And the
interpretation of those tests has to take
into account the clinical context because
the interpretation will be inaccurate without
Most patients presenting with suspected lung
disease can be actually fully assessed using
simple lung-function tests such as a peak
flow, spirometry and a chest x-ray.
Lung function is actually vital for monitoring
chronic lung disease. So those patients who
have chronic lung impairment need monitoring
over time to see whether that impairment is
staying stable or deteriorating. And that’s
the role of lung-function testing. Mainly
spirometry but not just spirometry, occasionally
transfer factor as well.
More complex diseases do require more complex
investigations with more detailed lung-function
testing – such as the transfer factor and
the lung volumes and, potentially a CT scan.
For some lung diseases – mainly lung cancer
– obtaining histology is vital and essential
to actually confirm the disease and to guide
therapy. And nowadays we have a multitude
of different methods for obtaining histology
from suspected lung cancer patients which
allows us to do this in the vast majority
of patients safely and quickly.
And thank you for listening.