Gary Thorpe: we are entering an exciting stage of new technologies |
A session on point-of-care diagnostic testing began with an
overview of the science behind the tests and a look at technologies in
development.
Gary Thorpe, of the Wolfson Research Laboratories, University of Birmingham,
explained that point-of-care testing is applied in many different disciplines
and that many different types of tests are available. “They are
bringing down the cost of manufacture so that you can now throw away
instruments,” Dr Thorpe added.
A simplified look at the science behind point-of-care tests revealed
that they work by three main mechanisms:
· Specific chemical reactions
· Specific enzymes
· Specific antibodies
Dr Thorpe explained that with all of these reactions, a colour change
is monitored or a device is used to produce a current or voltage which
is then measured. Generally, all the reactions are dry-phase reactions
and some kind of strip or electrode is used.
Moving on to recent developments, Dr Thorpe described a non-invasive
continuous glucose monitoring system that might be available in the future.
It is in the form of a disposable biosensor on the back of a watch. The
test works by reverse iontophoresis: a small current is applied to the
surface of the skin through which ions are dragged. Electrochemical detection
can then be used to measure glucose levels every 20 minutes. The biosensor
needs to be replaced twice a day. Dr Thorpe pointed out that the system
was not perfect; users have to wear the watch for three hours to equilibrate
it with their skin and a finger prick sample is still necessary in order
to calibrate the system.
“We are entering an exciting stage of new technologies, assays and
applications which will become commercially available and I think that
it will have
an important impact on health care, the biotechnology industry, pharmacies
and the general public,” Dr Thorpe concluded.
Pharmacogenetic testing
Pharmacogenetic testing can be used to predict a patient’s ability
to metabolise a drug and this information can help to reduce the incidence
of adverse drug reactions.
“The process of ‘take a pill and come back if you have a problem’ clearly
is back to front. We should really be looking to a future where we, and
the pharmaceutical industry, look to tailor the medication far better
to the needs of the patient,” said Paul Debenham, director of life
sciences at LCG, an independent analytical laboratory.
He told participants that the US Food and Drug Administration has started
to prompt pharmaceutical companies to introduce pharmacogenetic data
into their clinical trial dossiers. The FDA is focusing on a small number
of genes that it considers are valid, for example, CYP2D6. This gene
has a mutation called *4, which inactivates an enzyme in the liver and
reduces a person’s capability to metabolise a vast range of drugs.
Dr Debenham explained that people with this mutation are at risk of suffering
adverse reactions since the recommended dose is determined in clinical
trials using subjects who metabolise the drug at a normal rate.
The challenge has been how can we take pharmacogenetics from the laboratory
to the GP practice, said Dr Debenham. Traditionally, pharmacogenetic
testing has been conducted in laboratories by extracting DNA from a sample
of blood, saliva or urine and analysing it. He explained that several
companies are currently developing a system of direct sample analysis.
This means that the sample can be analysed in one step, without the need
for DNA extraction. In a system that LCG is developing, target amplification
and sample analysis can be carried out in 16 minutes, said Dr Debenham,
but it should be possible to speed this up in the future. The instrument
used is the size of a shoe box and it is capable of analysing 12 samples
at one time; this could be 12 samples from different people or 12 different
tests on one sample. The cost will be in the region of pounds (rather
than hundreds of pounds) per test, and the instrument itself will be
far cheaper than the necessary laboratory equipment. Dr Debenham told
participants that LCG is currently in discussions with a manufacturer
and hopes that it will be less than five years until this sort of technology
reaches the marketplace. |
The
Pharmaceutical Journal