A new easy-to-calculate score can predict the mortality risk and guide clinical decisions for coronavirus disease patients with greater reliability and ease than existing scoring systems, doctors said on Wednesday after the world’s largest study of Covid-19 patients.

The team of UK doctors has proposed a scoring system that relies on eight key health parameters that could be used to assign Covid-19 patients scores from 0 up to 21 with the probability of death increasing with rising scores.

The doctors said their 4C (Coronavirus Clinical Characterisation Consortium) Mortality score uses readily available data to accurately categorise patients as being at low, intermediate, high or very high risk of death but would need to be validated in more populations.

“We believe this scoring system is ready for use now — but we’d be happy to work with colleagues in other countries such as India to validate it,” Calum Semple, professor of outbreak medicine and child health physician at the University of Liverpool, told The Telegraph over phone.

Semple and his colleagues designed the risk assessment tool using data from over 35,400 Covid-19 patients admitted to hospitals across the UK between February and May who met the criteria for one of the four categories of risks.

The researchers — also based in universities in Edinburgh and Glasgow and the Imperial College, London — then tested and confirmed the utility of the tool on an additional 22,000 patients admitted in hospital during May and June. They have published their findings in the British Medical Journal.

The tool uses a Covid-19 patient’s age, sex, number of underlying health disorders, breathing rate, oxygen saturation level, Glasgow coma scale score — a measure of impaired consciousness, if any, based on eye, motor and verbal responses — urea, and C reactive protein, a marker of inflammation, to assign scores.

Patients with scores of 3 or lower have only 1 per cent probability of death, but the probability increases with rising scores — 22 per cent for score 10, 50 per cent for score 15, and 80 per cent for score 20.

“We expect this tool might help doctors to look at these scores and decide how to manage patients,” Semple said. A low score would provide reassurance to a doctor but a high score might alert a doctor to the need for rigorous observation and preparations for aggressive treatment, he said.

“This looks good and interesting,” said Anjan Trikha, a professor of anaesthesiology and critical care medicine at the All India Institute of Medical Sciences, New Delhi, who was not associated with the UK study but is chairperson of the AIIMS Covid-19 clinical management team.

Although doctors worldwide are already using several health and biochemical parameters to assess the mortality risk of Covid-19 patients, the UK researchers believe their tool outperforms most others.

Critical care specialists in India said the tool could help in triage — the process of separating patients into those who can be treated at home, in a ward, or in an intensive care unit.

“The advantage of this tool is that it is based on a very large number of patients — both in its design and validation,” said Sumit Ray, a critical care medicine specialist at the Holy Family Hospital, New Delhi, another doctor on India’s Covid-19 frontlines.

The study emerged from a network of clinicians and researchers who have been preparing for outbreaks since 2012 involving 260 hospitals across England, Wales and Scotland.

“These results highlight the benefit of being prepared in advance for the emergence of new pandemics such as Covid-19,” Fiona Watts, executive chair of the UK’s Medical Research Council, said in a statement released by the University of Edinburgh.