Diagnostics
management of STIs, especially in peripheral and resource-constrained settings.5 Engaging patients in the self-collection of
stool samples is more challenging. A qualitative study reported in the British Journal of General Practice looked at patients’ perspectives on providing a stool sample to their GP. It found barriers to collection included embarrassment, fear of results, concerns around hygiene and contamination, discretion and privacy, and lack of information.6
A separate study focused
on reasons for non-uptake of the NHS bowel cancer screening programme reported that: “Participants described sampling faeces and storing faecal samples as broaching a cultural taboo, and causing shame. Completion of the test kit within the home rather than a formal health setting was considered unsettling and reduced perceived importance.”7
Technical factors Issues with the quality of specimens can hinder effective PoC diagnosis too. Under- and over- sampling can be a problem when samples are not collected by a trained clinician, which may prevent an accurate result from being obtained. Sample contamination is another problem. For instance, if external bacteria on the skin are unintentionally captured in a sample, a misleading result may be generated. With regard to blood collection, venepuncture is the gold standard for the reliable provision of high-quality samples. However, this method generally requires a phlebotomist, so it is rarely feasible in a PoC scenario. Capillary blood collection is a common alternative to venepuncture when smaller volumes are sufficient. This is usually conducted using a fingerstick, so self-collection is possible. There are drawbacks to this method though when it comes to diagnostic testing. These include the risk of contamination, as well as haemolysis of the sample, which happens when red blood cells rupture. It can also be difficult to obtain the required volume. Nevertheless, several existing PoC diagnostic
tests, which accept whole blood, use the finger prick method and have an integral blood collection capability. In some cases, a collection device is used to both obtain the sample and transfer it into the test cartridge. Disadvantages associated with the finger
prick method are that it can be painful and messy. A new wave of minimally invasive capillary blood collection devices offers an alternative approach. Usually applied to the upper arm, they are user activated with a push-button and typically collect between 0.2 and 1ml of blood in under ten minutes. Examples include the YourBio TAP II device which uses a microneedle array to make an incision to the skin and the Drawbridge Health device which uses tiny lancets and vacuum technology to pull blood from capillaries onto a storage matrix within a removable cartridge. Loop Medical uses a similar vacuum-based technique to collect larger volumes of 1ml. So, what about urine collection? As a carrier
of hormones, cells, proteins, and bacteria that the body is eliminating, urine is a valuable diagnostic specimen. In terms of infectious diseases, it is routinely used in the diagnosis of STIs, and it is also listed as a suitable specimen
Sample collection holds a huge amount of untapped innovation potential. Obtaining specimens can be difficult for various emotional and technical reasons, and this appears to be particularly true of blood, urine, and stool samples. Exploration of this area should be firmly on the agenda of diagnostic companies looking to enter or expand in the PoC space.
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for the PoC diagnosis of TB in the DR-TB report mentioned previously. The authors explain that urine is an attractive fluid for rapid molecular assays because it is “easy to collect compared to other fluids such as sputum and serum, is readily available, and contains TB-specific proteins and DNA in patients with TB.” However, the assumption that urine is easy to collect can be a hindrance. There is no standard device for its collection beyond simple cups and funnels or tubes. Yet obtaining a suitable, clean sample is not always straightforward and inconsistent quality is a limiting factor in the development of urine-based PoC tests that could accelerate diagnoses and improve infection control. Urine sample contamination rates in the UK range from 0.3% to over 70%.8 Some tests, such as those for STIs, require
‘first catch’; the first 30ml of the first morning urine. It is used when epithelial cells and debris from the urethra are needed for analysis. Controlling the flow of urine to collect the right portion for the sample is difficult for many people. Trying to capture just the first 30ml, or indeed avoid it for a mid-stream sample, is a significant challenge for anyone with bladder control issues. This problem becomes more prevalent as we get older, or for women post pregnancy.
Oversampling can also be a major issue.
Flooding the lateral flow strip of an instream urine diagnostic device risks a false negative. When it comes to samples collected in a tube, overflow is common. At best this is messy, unhygienic, and potentially embarrassing for patients. It can also dilute first catch samples, reducing the effectiveness of testing. For diagnostic tests requiring a bacterial culture, cross contamination of the sample is a problem. This can occur if the sample runs off the patient’s legs before it is caught in the tube, and
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