Diagnosing flu at home: are we nearly there?

The current diagnosis of influenza infection (flu) in a general practice setting is on clinical grounds. This means that the doctor seeing the patient assesses the type of symptoms the patient is presenting, along with examination findings and the risk of an influenza infection based on the current prevalence of the illness in the community (usually between the months of December and March).

The common manifestations of flu are fever, headache, muscle aches, cough, sneezes, sore throat, and sometimes gastrointestinal symptoms such as vomiting or diarrhoea. In the future, there will undoubtedly be a more widespread point of care tests rolled out into the GP’s surgery. Expert consultant in respiratory and general medicine Dr Ben Marshall explains the future of diagnosing flu and whether home testing could lower infection rates or not. 
 

What kind of scans or testing is involved?

In primary care currently, there are no special additional tests at the GP’s disposal, except in a few practices which submit throat swabs to the Health Protection England surveillance laboratories. In hospitals these days, there are various points of care tests which can be done when the patient presents to the emergency hospital and are normally turned around within 24 hours. These molecular tests will also include other commonly circulating respiratory viruses, thus given the clinician immediate and useful clinical information to help treat the patient.
 

Can a diagnosis be made on the basis of these tests alone – or is a medical history important as well?

A detailed medical history is also useful not just in giving clues to the type of infection, but also to determine risk factors that might indicate those at risk of a more severe outcome from their influenza infection. Interestingly, we now know that influenza infections can cause a whole range of manifestations and severity of symptoms. For example, clinical studies suggest that up to a quarter of influenza infections in healthy persons may have few if any symptoms at all, and yet these individuals are infectious to others.
 

Could “home testing kits” be a reality one day? How could it work?

This might be possible but in reality, for most people, early diagnosis doesn’t really alter the outcome. Receiving immediate antiviral antibiotics (Tamiflu), for example, might only shorten the illness by 24 hours in an otherwise fit individual. However, early diagnosis in an at-risk population, for example, a frail elderly person living in a nursing home, might allow the provision of early preventive antiviral drugs to stop the spread of infection into an outbreak.
 

Would someone be able to get a prescription from test results obtained at home? Are there any current examples of this (e.g. STI testing)?

In theory, yes this might be possible, but outside of a pandemic or in those individuals at risk of more severe outcome from influenza, it wouldn't be a cost-effective initiative. There are other examples of home testing which work for the patient’s and the population’s benefit. For example, home testing for HIV infection and the bowel screening programme looking for occult in faeces (poo) have both been shown to speed up earlier diagnosis.
 

If this became a reality, how do you think this would affect infection rates?

I think it would be far better to concentrate on designing improved flu vaccines to reduce infection rates and limit transmission of influenza, as the recent introduction of the new nasal spray vaccine in children to protect against flu.