Rapid diagnostics are reshaping infectious diseases care, but their value depends on more than speed alone. With insights from the recent BSAC New Agents Conference, Gerry Hughes examines the current landscape, evidence for clinical impact, barriers to adoption and where the next advances may emerge.
At some stage in almost every suspected infection, the clinician must answer three practical questions: is this truly an infection, what pathogen is involved, and what treatment is most likely to work? Within that uncertainty lies hope that the microbiology laboratory can help bring clarity.
In practice, however, gaps exist in the paradigm of specimen collection, pathogen identification, antimicrobial susceptibility testing and resultant treatment. During this interval, broad empirical antimicrobial therapy is commonly started to avoid the consequences of undertreating serious infection.
Although often necessary, this approach can expose patients to broad-spectrum agents when infection is absent, the pathogen is resistant or narrower therapy would suffice.
Rapid diagnostic technologies have the potential to optimise the infection treatment process. By providing faster, more precise microbiological data, they can support earlier optimisation of antimicrobial therapy. This is especially important as antimicrobial resistance (AMR) threatens the medicines on which modern healthcare depends.
This tension between technological promise and real-world impact formed the context for a recent appraisal of the rapid diagnostics landscape presented at the British Society for Antimicrobial Chemotherapy (BSAC) New Agents Conference by Dr Timothy Rawson, clinical associate professor in infectious diseases and antimicrobial resistance at Imperial College London.
Dr Rawson opened his presentation by framing the promise of rapid diagnostic technologies in terms of their potential to ‘protect new agents when they come online for use in clinical practice. Clearly having available diagnostics and integrated stewardship approaches to maximise their efficacy and lifespan is of critical importance’.
The current diagnostics landscape
Clinical microbiology is undergoing rapid change, with diagnostic health technologies increasingly reshaping how infection is detected, characterised and managed.
Molecular diagnostics, rapid susceptibility platforms, genomic sequencing and laboratory automation are generating larger volumes of clinically relevant data and creating opportunities to integrate diagnostics more directly into treatment decisions, stewardship activity and health policy.
Many molecular diagnostics can deliver results far more quickly than culture and, in some cases, they offer greater sensitivity. However, evidence of consistent downstream benefit on patient outcomes, prescribing practice and antimicrobial resistance has been mixed. One reason is that molecular tests provide a genetic snapshot, whereas clinicians often still need phenotypic data to judge whether an antimicrobial is likely to work in practice.
This distinction matters. For example, a negative multiplex polymerase chain reaction (PCR) result cannot definitively exclude bacterial infection because target panels do not capture every possible pathogen.
Similarly, these tests cannot always identify the optimal treatment because they do not fully describe organism phenotype. For this reason, molecular diagnostics for bacterial infection currently complement rather than replace conventional culture-based methods.
Their value is greatest when they shorten time to clinically useful information and support earlier treatment decisions. However, speed is not the only factor, but whether results are interpreted correctly and translated into prescribing change.
In practice, this means the greatest impact of rapid diagnostics is likely to be seen when they are embedded within antimicrobial stewardship (AMS) pathways rather than used as standalone tests.
Rapid diagnostics applied within secondary care
Evidence from secondary care suggests that rapid diagnostics can improve key process and service outcomes, although their effect varies by clinical context and by whether they are paired with AMS support.
A recent systematic review and meta-analysis of rapid multiplex PCR for respiratory viruses in adults with acute respiratory illness included 27 studies and more than 17,000 patient encounters. The intervention shortened time to results by approximately 24 hours and was associated with a modest reduction in hospital length of stay.
Among patients with influenza, rapid testing also increased appropriate antiviral use and improved use of infection control facilities. However, the review did not show a clear effect on antimicrobial prescribing or mortality, and economic findings were inconsistent.
A second large review examined rapid diagnostics for organism identification in bloodstream infections, covering 88 studies and more than 25,000 patient encounters. Here, the most important finding was that rapid diagnostics delivered alongside an AMS programme were associated with lower mortality, shorter hospital stay and faster time to optimal therapy compared with blood culture alone.
By contrast, rapid diagnostics used in isolation did not show the same survival benefit, and AMS support without rapid diagnostics was also insufficient to produce comparable effects.
Therefore, the evidence clearly suggests that rapid diagnostics are most effective when embedded within a responsive AMS model that can translate timely microbiological information into earlier treatment optimisation.
This was a point iterated by Dr Rawson on several occasions during his talk. ‘It’s clear that no one intervention is likely to have an overwhelming impact on the decisions which we make,’ he said. ‘We try and assess the value of our diagnostic tests around AMS often as isolated interventions. And what this means is it becomes difficult to assess the true value of our diagnostics in clinical practice.’
Barriers to rapid diagnostic adoption
Several barriers continue to limit wider adoption of rapid diagnostic tests in infectious diseases, with cost being one such unavoidable example.
Rapid tests, especially molecular platforms, are often viewed as expensive compared with conventional laboratory methods. Upfront costs may be offset by downstream savings through faster treatment optimisation, fewer unnecessary cultures and more appropriate antimicrobial use. However, such savings may not be immediately apparent.
Reimbursement models also vary between countries, influencing whether rapid diagnostics are financially viable in practice. More broadly, uptake depends on more than the test itself. Without stronger setting-specific clinical and economic data, many health systems will remain reluctant to invest at scale.
Heterogeneity and gaps in evidence have contributed to cautious uptake and relatively limited endorsement in professional guidance.
Although rapid diagnostics are widely seen as promising, published data remain concentrated in a small number of settings, particularly bloodstream infections and high-income countries, leaving important gaps across other syndromes, regions and healthcare systems.
Downstream implementation barriers inevitably arise, and prescribing behaviours can be difficult to change. Successful adoption requires education, communication, logistics, laboratory-clinical integration and stewardship support.
Dr Rawson set out the four key questions he believes clinicians and healthcare commissioners should be asking when it comes to rapid diagnostics:
- After generating your high-quality evidence and clearly defined populations or intended use, we move on to this challenge around how do we actually integrate these tools into our local pathways?
- Do we have to develop new stewardship programmes, or can they fit into the resources we have available to us?
- How do we deliver things like quality assurance?
- And – probably most importantly – how do we actually fund these and ensure that they're cost effective for us locally?
He also advised that local implementation needs to be considered carefully and may be the final hurdle in adopting a new rapid diagnostic technology for infection.
In the broader context, antimicrobial prescribing is not a single decision but a sequence of linked judgements, each shaped by multiple clinical, microbiological and organisational factors, he said.
Innovations in rapid diagnostics
Despite these barriers, innovation continues, particularly for common, high-volume infections such as urinary tract infection (UTI).
A recent UK study evaluated a rapid direct-from-urine phenotypic antimicrobial susceptibility test – an important development in a setting where around 65 million urine samples are tested annually in the UK alone.
Rapid microcapillary direct-from-urine testing was compared with reference broth microdilution in 352 remnant urine samples. As the commonly used boric acid preservative in UTI samples potentially interferes with direct-from-urine tests, 90 paired samples were also processed with and without boric acid preservative.
In samples containing a single organism, the rapid test achieved 96.95% concordance with the reference method, across seven first-line UTI agents.
Mean time to result was 5.85 hours – faster than standard susceptibility testing. Agreement between paired samples with and without boric acid was 98.75% (158/160), suggesting that preservative use did not materially affect performance.
These findings suggest the method could deliver same-day susceptibility results from routinely collected urine without complex processing.
Commenting on this innovative test at the time the paper was published, Professor Mike Lewis, National Institute for Health and Care Research (NIHR) scientific director for innovation, said: ‘This NIHR-funded research not only has the potential to deliver quicker, more effective treatments to patients suffering with UTIs, but also tackles the broader challenge of AMR.
‘The rapid urine test is a fantastic example of the real-world solutions to AMR that the Government committed to developing in its 10-Year Health Plan.’
Conclusion
Rapid diagnostics are increasingly capable of delivering faster, more precise information. But speed alone is not enough. As a recent editorial in the journal Clinical Microbiology and Infection argues, diagnostics should not be judged on availability alone if clinical context and downstream consequences are ignored.
It is also notable that several infectious disease domains remain underserved by diagnostics including parasitic infections, sexually transmitted infections, drug susceptibility testing for tuberculosis and appropriate serological testing practices.
Available evidence for rapid diagnostics is skewed towards high resource settings. Low- and middle-income countries, where infrastructure, cost and access often shape diagnostic choices more so than technological availability, remain insufficiently represented. This is despite these regions having some of the greatest need for pragmatic, high-impact diagnostic strategies.
The most promising advances in rapid diagnostics will be those that fit real clinical pathways, support AMS in practice and answer the questions that matter most at the bedside.