Authors: David Padley (the NIBSC; Potter’s Bar, UK)
Point-of-care (PoC) tests are designed to provide an alternative diagnostic at times when time, resources or infrastructure might mean that samples can’t be analyzed in a clinical diagnostic laboratory. Despite their popularity, especially in diseases such as HIV, these devices might not be amenable to external quality controls, a factor that could cast doubt on their results.
To find out more about this topic we spoke to David Padley from the National Institute for Biological Standards and Control (the NIBSC; Potter’s Bar, UK), a part of the Medicines & Healthcare products Regulatory Agency (MHRA), about his recent poster ‘Point-of-Care testing for HIV: specialist quality control materials are a necessity’, presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID; 11–16 April, Amsterdam, the Netherlands).
First, could you introduce yourself and give a brief summary your career to date?
My name is David Padley, I currently work for the NIBSC and I have been working in diagnostics since 1996. I first started off working in TB diagnostics and then moved into food-borne pathogens. I joined the NIBSC in 2000 where I started working on hepatitis viruses, and then moved into some work with malaria and toxoplasma doing assay design and producing international standards that are currently being used. Then in 2010, I became head of the Quality Control Reagent’s Unit, which is part of the division of Infectious Disease Diagnostics. What we do is we produce quality control reagents for serology assays. We have on record approximately 40 separate reagents and covering disease such as hepatitis, HIV, toxoplasmosis, syphilis, Lyme disease and others.
Could you outline the research you’re presenting here at ECCMID?
So, in the study that we have just undertaken we wanted to see if our current quality controls, which we produced for ELISA & CLIA assays, would be suitable to use for the quality control of PoC testing. We took 12 separate devices and we assessed them using our controls – a high control, a medium control and a low control. What we discovered was that some devices work slightly better than others, but generally that using these controls wasn’t suitable for use for PoC testing. However, we do produce a HIV-1 control that is specific for rapid testing devices and this was positive in all of the devices that we used.
Moving on from that we decided to look at the limits of detection using clinical samples. To do this we used the master stocks that we make of HIV-1 and HIV-2 reagents, in addition, we had two further HIV-1 clinical samples that we obtained from the National Blood Service (UK). We carried outdid limiting dilutions to allow us to compare the devices against each other. Again, we discovered that some were better than others – which you get in every assay – but generally we discovered that the detection of HIV-2 wasn’t as good as the detection of HIV-1.