This is a plain English summary of an original research article
Rapid tests for flu led to more timely treatment with antiviral medicines for people in hospital. New research found that people with suspected flu who had rapid tests were less likely to become seriously ill than those receiving standard care. They were also transferred to isolation more quickly, which could reduce the spread of infection.
Researchers at the University of Southampton used rapid tests (called molecular point-of-care tests) which give results in less than an hour. They tested hospital patients with suspected flu during the flu season. The researchers recommend that these rapid tests should be used during the flu season for people in hospital with respiratory symptoms.
Most people recover from the flu in around a week and do not need treatment. But some groups are more likely to develop serious illness and experience complications such as chest infections and pneumonia. In 2017/18, more than 22,000 people are thought to have died from flu. Elderly people, pregnant women, those with weakened immune systems, and people with certain long-term health conditions are at high risk.
Hospital patients who have flu may benefit from antiviral treatment to reduce the severity of their illness. But they often remain undiagnosed. Many are never tested and others have tests with long turnaround times. The result is that many people with flu do not receive antiviral treatment early enough, nor are they isolated to prevent spread of the virus.
This research found that rapid tests for flu are effective and the researchers recommend their use in hospitals during the flu season.
What’s the issue?
Flu can be a serious illness, especially for elderly people and those with weakened immune systems. Every year, during autumn and winter when the flu virus is circulating, large numbers of people are admitted to hospital with flu. Some (3% – 15%) die in hospital.
Despite this, flu often goes undetected in hospital because people admitted with severe respiratory symptoms are not always tested for it. Even when they are tested, it can take up to 24 hours to get the result of a PCR test back from the laboratory.
Clinical guidelines say that patients in hospital with flu should be given an antiviral treatment called a neuraminidase inhibitor. Giving this medicine early increases the chance of recovery and shortens the stay. But a lack of testing and delayed diagnosis means that many patients with flu are not identified, not treated appropriately, and not isolated in separate wards to prevent the spread of the virus.
Unlike laboratory tests, rapid molecular tests for flu give on the spot results in less than an hour. They are already used in some NHS hospitals and are highly accurate. There is some evidence that people with flu receive antiviral medicine sooner and there may also be less spread of the virus when rapid tests are used. However, before this study, there was a lack of high-quality evidence that the rapid test makes a positive difference for patients.
The research team explored whether rapid tests lead to improved detection, faster treatment, and more use of isolation. They also looked at how well hospital patients with flu recovered.
The FluPOC trial was run over two flu seasons (December 2017 to May 2019) and included 613 adults. They had all been admitted to two hospitals with severe respiratory symptoms. These symptoms could be a flu-like illness, pneumonia, bronchitis (infection of the lungs), or a flare-up of long-term conditions such as asthma.
Half the study participants had the rapid test. In the control group, the other half received standard care and had a standard flu test if their doctor felt it was necessary. In order to compare the two management strategies, this group also had a rapid test (but these results were not looked at until the end of the study).
The researchers recorded how soon patients with confirmed flu received medication, whether they were isolated, and how well they recovered.
In both groups, 1 in 3 people (33%) had confirmed flu.
The study demonstrated the benefits of the rapid test. It found that, with the rapid test:
- more patients (100%) were correctly identified as having flu, compared with 59% people in the standard care group
- almost all patients (99%) were given antiviral treatment within 5 days, compared with fewer (62%) in the standard care group
- antivirals were given earlier (in 1 hour on average, compared with 6 hours in the standard care group)
- isolation facilities were used more often (70% patients were isolated compared with 38% in the standard care group)
- isolation was in place sooner (after 4.5 hours on average, compared with 25 hours in the standard care group)
- patients were less likely to become seriously ill (with any symptom that was life-threatening, caused disability or led to a longer stay in hospital); 19 patients became seriously ill compared with 34 in the standard care group
- no flu patients died, (compared with 2 flu patients in the standard care group).
Why is this important?
The findings suggest that routine use of rapid tests for flu improves detection of the illness compared with standard clinical care. Flu testing is not routine in most hospitals. Clinicians may order a PCR test when they suspect flu, but this misses patients who do not show the classic symptoms of the illness.
When the rapid test is routinely used to detect flu, patients are likely to receive appropriate medication faster. They can also be swiftly isolated from others, which reduces the spread to other patients and staff in the hospital. People with flu who were diagnosed with the rapid tests were less likely to become seriously unwell.
The researchers say that more hospitals should replace laboratory-based PCR tests for flu with routine point-of-care rapid testing. The study took place during the winter months. This means the findings are relevant to flu seasons, and not necessarily to other times of the year.
The researchers say the evidence is strong enough to implement the rapid test for routine flu testing in all hospitals during flu season.
This study took place before the pandemic. Since then, the testing landscape has changed considerably. Many hospitals now use rapid point-of-care tests regularly for detecting the virus that causes COVID-19.
This research suggests it is feasible to expand the use of rapid hospital testing to include flu.
But there are still some uncertainties about the best way to carry out rapid testing. Specific questions include which hospital workers should perform the test. In Southampton, testing is run by nurses working in emergency and acute care, and author Tristan Clark recommends this approach, along with input from the laboratory.
Recent developments include newer tests which can give results even more quickly, within 20 minutes or less. And it could be that tests for multiple illnesses (such as both COVID-19 and flu) would be more useful. Further trials could address these questions.
Future research should look at the cost-effectiveness of rapid testing for flu and other illnesses. The researchers are intending to explore this, but their work is delayed due to the COVID-19 pandemic.
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This NIHR Alert is based on: Clark TW, and others. Clinical impact of a routine, molecular, point-of-care, test-and-treat strategy for influenza in adults admitted to hospital (FluPOC): a multicentre, open-label, randomised controlled trial. Lancet Respiratory Medicine 2021;9:4
Earlier research on point of care tests for flu: Brendish NJ, and others. Routine molecular point-of-care testing for respiratory viruses in adults presenting to hospital with acute respiratory illness (ResPOC): a pragmatic, open-label, randomised controlled trial. Lancet Respiratory Medicine 2017;5:401-411
A trial looking at the impact of point of care testing on infection control: Brendish NJ, and others. Clinical impact of molecular point-of-care testing for suspected COVID-19 in hospital: A prospective, interventional, non-randomised, controlled study (COV-19POC). Lancet Respiratory Medicine 2020;8:1192-1200
Funding: This research was funded by the NIHR Post-Doctoral Fellowship Programme and was supported by the NIHR Southampton Respiratory Biomedical Research Centre and the NIHR Clinical Research Network, Wessex.
Conflicts of Interest: Some of the authors received speaker and consultancy fees and free equipment from biotech and pharmaceutical companies who manufacture molecular point-of-care tests.
Disclaimer: NIHR Alerts are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that views expressed in NIHR Alerts are those of the author(s) and reviewer(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.