The NHS’s 111 online symptom checker for coronavirus isn’t “up to the task”, according to a new study, which warns some people with severe Covid symptoms may have been incorrectly told to stay home, rather than seek medical help.

The digital triaging tool, which asks users questions about their symptoms as well as details such as their gender and age, advises on the most appropriate course of action from a set of pre-determined responses.

It’s one of several online ‘symptom checkers’ for Covid-19 that has been rolled out across the globe.

But as yet, there’s hardly any evidence for the effectiveness of these checkers for prioritising – or triaging – patients for treatment during a pandemic, say researchers. 

The report, published in BMJ Health & Care Informatics, suggested digital Covid-19 ‘symptom checkers’ may stop some patients from getting prompt treatment for serious illness.

Researchers studied the efficacy of national government-sponsored digital symptom checkers used in Singapore, Japan, the US and the UK to triage people in need of a medical assessment and/or treatment correctly.

Both the US and UK symptom checkers “consistently failed to identify” the symptoms of severe Covid-19, as well as bacterial pneumonia and sepsis, frequently advising those with serious cases to stay home, the findings indicated.

However, NHS Digital says the symptoms checker is “not a diagnostic tool” and has been updated since the study took place. 

Researchers looked at four trackers including: the Singapore Covid-19 Symptom Checker; Stop Covid-19 Symptom Checker (Japan); CDC Coronavirus Symptom Checker (US); and 111 Covid-19 Symptom Checker (UK). 

Covid-19 death rates in Singapore and Japan are comparatively low compared to the US and the UK.

The study was designed to see if symptom checkers were able to differentiate mild cases of Covid-19 from severe ones – and how well they picked up Covid-19 ‘mimickers’, such as bacterial pneumonia and sepsis in 52 case scenarios.

Those cases simulated common Covid-19 symptoms of varying severity and risk factors. These included: cough and fever; a co-existing condition (such as high blood pressure) plus cough and fever; suppressed immunity as a result of drug treatment plus cough and fever; and shortness of breath and fever. 

The symptom checkers in Singapore and Japan triaged twice as many cases for direct clinical assessment as the symptom checkers in the US and UK. Singapore had the highest overall referral rate at 88%; the US the lowest at 38%; while the UK had the second lowest at 44%. 

The online NHS 111 symptom checker “frequently” advised those with possibly severe Covid-19 and bacterial pneumonia to “stay home” with no follow-up, the researchers said, and is likely to have delayed treatment for sepsis, severe Covid-19, and severe sepsis.

The UK’s symptom checker was singled out for its complex algorithm, and for attempting to quantify symptoms such as shortness of breath and the overall severity of illness by asking subjective, qualitative questions with multiple choice answers. The questions used to discriminate between degrees of severity “aren’t up to the task”, the study suggested.

Researchers acknowledged that by reducing physical contact, online symptom checkers can save valuable resources and reduce viral spread, and noted they require fewer resources than phone and telemedicine triaging services.

However, they warned that some symptom checkers (including the NHS 111 checker in the UK) “are likely to delay presentations of serious medical conditions to appropriate care, and as such, are likely to confer an increased risk of morbidity and mortality”.  

Responding to the study, NHS  Digital told HuffPost UK “NHS 111 online is not a diagnostic tool”.

“It allows people to assess their symptoms and signposts to other NHS services as required,” a spokesperson added. “This simulation study was based on an early version of the tool. Over the past year it has been continually revised and updated in response to new scientific information, government guidance and public health strategies.”

HuffPost UK has also contacted The Department of Health and Social Care in relation to the study and will update this article when we receive a response.