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 21 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,