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Discovery of four COVID-19 risk groups will help guide treatment

Published: 10 September 2020

People who are admitted to hospital with COVID-19 can be divided into four distinct risk groups and offered treatment accordingly, show data from the world’s largest study of patients with the disease.

Researchers identified the groups using clinical information and tests carried out on patients at arrival at hospitals across England, Wales and Scotland. The data collected were then used to predict the patients’ risk of death – ranging from low to very high.

A COVID-19 risk identification tool – the most accurate to date – has been designed using these groupings, to help clinical staff choose the best course of treatment for patients admitted to hospital. 

The tool was built by the ISARIC Coronavirus Clinical Characterisation Consortium, which has been funded by the NIHR and UK Research and Innovation.

Data from 35,000 patients admitted to hospital between February and May 2020 were used to understand risk groups and develop the new tool, which has been published in the British Medical Journal

Some of the data used to identify which group a person falls into – and, therefore, their risk of dying – included age, sex, the number of pre-existing conditions, respiratory rate on admission, and the results of two blood tests. 

One in every hundred patients in the low risk group was found to be at risk of dying. It was 10 in a hundred patients in the intermediate risk group, 31 in a hundred in the high risk group and 62 in a hundred in the very high risk group.  

The tool was then tested and confirmed to be accurate using information from a further 22,000 patients hospitalised from the end of May to the end of June 2020. 

The risk categories could be used to support treatment decisions, such as admitting patients at high risk to critical care straight away. Dr Stephen Knight, Co-Lead Author and NIHR Clinical Research Fellow at the University of Edinburgh, said: “This accurate and simple risk identification tool, applicable across all groups within society, will help detect at risk individuals quickly on arrival to hospital. As importantly, we will be able to reassure and potentially treat at home those patients who fall within the low risk group.”

Until now there has not been an accurate risk tool for COVID-19 patients. Existing tools for pneumonia or sepsis do not offer accurate predictions due to the differences between diseases. 

Previous attempts to build a risk prediction tool for COVID-19 have had limited success due to small sample sizes and lack of formal validation. One limitation of this new tool, however, is that it can only be used on hospital patients and not within the community.

Minister for Innovation Lord Bethell said: “Protecting the most vulnerable from COVID-19 is a priority, which is why we’re supporting valuable research like this to help doctors make the best possible decisions for NHS patients. I am delighted to see my former university leading the way on it.

“We look forward to seeing how this new tool can help clinicians target treatments more effectively for coronavirus patients admitted to hospital now and in the future, potentially saving countless lives.”

The work is the latest results from ISARIC – a global network of clinicians and scientists who have been preparing to prevent disease and death from severe outbreaks since 2012 in readiness for a pandemic such as this.

The ISARIC 4C study involves 260 hospitals across England, Wales and Scotland and two thirds of all people admitted to hospital with COVID-19. The NIHR Clinical Research Network has recruited almost 78,000 participants to the study, following its prioritisation through Urgent Public Health status.

Professor Calum Semple, Chief Investigator and Professor in Outbreak Medicine and Child Health at the University of Liverpool, said: “This winter is likely to see great pressures on our health services, with staff being redeployed to less familiar acute care areas. 

“In these difficult circumstances the 4C mortality score is likely to be a valuable tool for supporting decisions that allow prompt escalation of care to those most likely to benefit. The scale of success of the ISARIC 4C study is testament to the group’s commitment in preparing for pandemic public health research.”

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