HHE Pathology and diagnostics supplement 2018 | Page 21

Prepared faecal sample
added into slot
Test window showing
coloured line for ‘C’ (control)
but no reaction for ‘T’ ( test)
Figure 2 shows a clean area, a designated cabinet,
sterile equipment and laboratory coats that are
only used in that room as required. In recent
years it has proved possible to scale down the
amplification systems into a small desk top
analyser. The person operating the test simply has
to load the sample into the machine and all the
necessary steps are carried out inside it. Thus, as
with LFA, all that is needed is suitable training;
scientific understanding of the principle or
technical ability to interpret the data are not
required. The time it takes to achieve a result
varies, but is usually one to three hours.
Use of POCT devices in diagnostic virology
The LFA format has proved quite useful in the
main virology laboratory. For example, to confirm
a new diagnosis of human immunodeficiency
virus (HIV) infection, the blood sample needs to
be re-tested using a number of different types of
assay, which could include a POCT kit. Before PCR
was widely available, it was common to test
respiratory samples for respiratory syncytial virus
Figure 1
Lateral flow device for
detection of norovirus in
a faecal sample (virus not
detected)
Figure 2
Scientist preparing sample
prior to nucleic acid
amplification analysis
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HHE 2018 | hospitalhealthcare.com
(RSV) or influenza virus by LFA before cell culture,
in case it could provide a preliminary result. More
recently, they have found an application in
reconfigured laboratory services, where a main
laboratory at one site serves several other
hospitals. Using POCT (LFAs and molecular
analysers) in the smaller ‘satellite’ microbiology
departments has proved very successful. The
turnaround time for many specimens will be
relatively fast and the number of specimens
transported to the main laboratory will be
reduced. 4 With full training, this function could
be performed by laboratory staff who do not
usually work in virology. Another situation
where POCT could be useful is for unusual
infections for which a main laboratory assay is
not routinely available, but a rapid result is
desirable (for example testing for Ebola virus). 5
One obvious application of POCT in the ‘near
patient’ setting would be screening of patients in
hospitals during outbreaks of norovirus or RSV,
prior to cohort nursing. Laboratory scientific staff
can be involved in the testing, but the idea would
be for other healthcare workers to do the tests
and take responsibility for recording the results.
While LFAs have been widely evaluated for this
purpose, it should be noted that performance can
be quite variable. Although most kits are found to
have high specificity (meaning a positive result
can be taken as accurate), sensitivities are often
less than 90% (which means that one in ten tests
could give a false negative result). When it is
important to identify exactly which paediatric
patients do actually have RSV (and which have a
different respiratory infection), the main
laboratory PCR test can be a more clinically
acceptable and cost effective option. 6 It should be
feasible to obtain a result within one working day
and commercial PCR kits that allow testing for
several pathogens in one assay (multiplex PCR)
are becoming widely available. In addition,