Canadian researchers have examined the accuracy of rapid influenza diagnostic tests (RIDTs) in a meta-analysis of 159 studies. The results, published in the Annals of Internal Medicine, revealed that although RIDTs can confirm the flu, they do not rule it out and that RIDTs are also better at identifying the influenza A virus, which is more common, than the influenza B virus. The results also showed that the accuracy of the tests is higher in children than in adults.
To provide the best patient care possible, and to control infection, it is crucial to diagnose influenza as quickly as possible. The gold standard tests for identifying influenza have been viral culture and reverse transcriptase polymerase chain reaction tests (RT-PCR). However, these tests can be expensive, with results taking from between one to 10 days.
RIDTs are trying to overcome these problems given that they are easy to use and provide results within 15 to 30 minutes without needing to be sent to a lab, as they can be administered in routine clinical settings, such as doctor’s surgeries or emergency departments in the majority of cases.
At present, there are over 25 rapid flu tests on the market, however the literature accompanying these tests is substantial in volume and needs to be evaluated by doctors and healthcare providers. Senior study author, Dr. Madhukar Pai, associate professor at McGill’s Department of Epidemiology & Biostatistics, and a researcher at the RI MUHC explains:
“This is exactly why we needed a meta-analysis. So many papers have been published, especially since the H1N1 pandemic, but no one had synthesized this body of literature into one single cohesive piece. Our hope is that this work will help in informing future guidelines on the use of these tests.”
In answer to the question as to what these study results mean for patient care, Dr. Chartrand explains:
“Our results suggest a case for routine implementation of these tests at the point-of-care, especially among children, during flu season. It would have to be shown in clinical practice, but the routine use of these tests could mean significant improvements in patient care, especially children.
For example, if you know your patient has the flu, you might not need to run other tests. Maybe you’d be able to prescribe antiviral medication earlier. And perhaps flu patients would be triaged differently and sent home more quickly, which is great news for high-traffic emergency rooms and clinics during the flu season. But it is important to note that rapid flu tests can be falsely negative and therefore should not be used to rule out flu.”
Depending on the severity of the season, the Public Health Agency of Canada estimates that influenza and its complications cause fatalities of between 2,000 and 8,000 Canadians per year, whilst the U.S. Centre for Disease Control estimates a death rate of between 3,000 and 49,000 people annually.
Study author Dr. Timothy Brewer, Director of Global Health Programs at McGill concludes:
“Influenza treatment is most effective when started early in the course of the illness. The ability to start specific influenza therapy sooner in persons at high risk for complications, such as pregnant women or individuals with heart disease, and who have a positive rapid test result, is a major benefit of these tests.”
Written by Petra Rattue