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Highlights from

The European Congress of Clinical Microbiology & Infectious Diseases

29th Annual Meeting

Amsterdam 13-16 April 2019

Do rapid diagnostic tests in respiratory infection reduce unnecessary antibiotic prescribing?

Take-home messages
  • New diagnostic tests are accurate but costly, so their use must be justified
  • There is evidence that rapid diagnostic tests do not reduce unnecessary antibiotic prescribing in respiratory infection
  • This could be due to a multitude of factors that influence prescribing behaviours, however
“We’re in the midst of an explosion of new rapid diagnostics, but we’ve got to really think hard about what added value they are bringing.”

Dr Sanjay Patel, Consultant in Paediatric Infectious Diseases, Southampton Children’s Hospital, UK

Presenters at this year’s European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), Amsterdam, debated whether rapid diagnostic tests in respiratory infection actually reduce unnecessary antibiotic prescribing.

Though the first presenter, Kate Templeton, Consultant Clinical Scientist in Microbiology, Royal Infirmary Edinburgh, UK, answered a firm “Yes, they do”, Dr Sanjay Patel, Consultant in Paediatric Infectious Diseases, Southampton Children’s Hospital, UK, disagreed.

“There is a lot of diagnostic energy at the moment. I don’t want to dispel it, but I want to bring an air of realism to it,” he told delegates at ECCMID 2019. Although the field of rapid diagnostics is expanding, he thinks that we need to question what value they actually add, considering the technologies generally come at a significant cost to the healthcare system.

Firstly, he spoke about the gravity of the unmet need that the tests are trying to address. “I don’t think anyone in this room is going to disagree that we do face huge challenges in terms of antibiotic resistance. We know that, if we prescribe inappropriately, as we are now, we are hugely fuelling that very uncontrolled rise in antibiotic resistance.” It is clear why we are throwing money at attempts to cut unnecessary antibiotic prescribing, as the long-term impact is, quite literally, of apocalyptic magnitudes.

Before we look at the tests, we need to think about where prescriptions come from, he says, and the majority are prescribed in primary care. “For coughs in the UK in the past 15 years, there’s been no downtrend in prescribing in primary care,” Dr Patel explained, saying that about 50% of patients will leave a consultation with an antibiotic. For sore throats, it is around 65%.

It makes sense, however. Primary care providers are under high pressure to work out whether an infection is viral, bacterial, or a co-infection, and they may prescribe antibiotics ‘just in case’ to avoid their patient coming to harm.

So, can rapid diagnostics change antibiotic prescribing behaviour? Dr Patel thinks not, recounting evidence from a study of rapid point-of-care testing (POCT) versus placebo in respiratory infection. In this study, 44.7% of patients in the POCT group had a respiratory virus detected versus 15.3% in the control group. However, 83.6% (n=301) versus 83.1% (n=294) of patients received antibiotics in the respective arms (p=0.84); it made next to no difference to antibiotic prescribing. Although POCT was associated with a reduced length of hospital stay, mean duration of antibiotic treatment was very similar between the two arms. With this, he warned clinicians to be critical of the positive studies they read.

“In terms of ecological impact of antibiotics, these extremely costly tests are doing nothing. And they should do - don’t get me wrong, the argument is obviously there,” he added, then addressing the question of why these tests are not working, despite their accuracy.

“It’s clearly because prescribing behaviour is complicated,” he said. We cannot underestimate how complex prescribing behaviours are. Influences may involve psychological factors, societal pressures, worries of litigation, the possibility of rapidly spread scrutiny on social media; it is making clinicians more risk averse, he argues, which may increase the likelihood of ‘just in case’ prescribing.

In order to tackle this issue, maybe it is a question of focusing on the behaviour itself, as opposed to rapid diagnostic tests. And perhaps treatment paradigms need to change too; antibiotics may not always be needed - even in bacterial infections - and a severity-based approach could be adopted instead, he argued.

If we address these issues, there are still some downsides to rapid diagnostics that need to be taken into account: there could be false positives or negatives, clinicians must be able to interpret the results correctly, and the time taken for the test to work could also disrupt patient flow.

“We’re in the midst of an explosion of new rapid diagnostics, but we’ve got to really think hard about what added value they are bringing.”

When looking to the future of rapid diagnostics, he explained that the tests should provide answers as to whether patients will benefit from antibiotics, they should provide results in a reasonable amount of time, and they should have robust evidence in the real world.

In a concluding remark, Dr Patel stated “Rapid diagnostics - they’re amazing, but actually, do they really impact on antibiotic prescribing? They definitely don’t… at the moment.”

Based on Patel S. Rapid diagnostic tests in respiratory infections: do they really help clinicians reduce unnecessary antibiotic prescribing? (symposium SY089). Presented on Sunday 14 April 2019.

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The content and interpretation of these conference highlights are the views and comments of the speakers/ authors.

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