People who have been infected with Covid-19 should not have pre-planned surgery for seven weeks after diagnosis to reduce their risk of death, researchers have said.

A new study, published in the journal Anaesthesia, examined death rates among patients across 116 different countries, including the UK.

Researchers from Birmingham analysed data on patients who had received a Covid diagnosis before their surgery and also looked at whether a person had died in the month after their operation.

They found that death rates were higher in the first few weeks after a diagnosis.

But after seven weeks the proportion of people who died post-surgery were the same as people who had not been diagnosed with coronavirus.

The authors also found that patients were more likely to have a higher risk of post-surgery death if they had ongoing symptoms of Covid-19.

Researchers looked at information on 140,231 patients – including data on patients from 205 hospitals across the UK.

This included 3,127 people who had been diagnosed with Covid-19.

Some 1.5% of people who did not have a coronavirus diagnosis before their surgery died within 30 days of their operation.

But among those who had surgery up to two weeks after their diagnosis, this rose to 4.1%.

And among those who had surgery three to four weeks after their diagnosis, 3.9% died within a month.

This dipped to 3.6% in those who had an operation between five and six weeks after diagnosis.

Surgery performed seven weeks after diagnosis had a similar mortality rate within 30 days of operation as those with no diagnosis of Covid-19.

The researchers said that, where possible, surgery should be delayed to mitigate risks.

They also examined whether people were more likely to have a higher risk of death if they had ongoing symptoms after their diagnosis.

Those patients with ongoing symptoms had a higher risk of death when compared with patients whose symptoms had resolved or who had been asymptomatic.

People with ongoing symptoms had a 6% risk of death within 30 days.

This compared with 2.4% among patients whose symptoms had resolved and 1.3% of patients who were asymptomatic.

The lead authors, Dr Dmitri Nepogodiev and Dr Aneel Bhangu of the University of Birmingham, suggested that patients with ongoing symptoms may benefit from a further delay.

“We found that patients operated on 0-6 weeks after Sars-CoV-2 infection diagnosis are at increased risk of post-operative death, as were patients with ongoing symptoms at the time of surgery,” said Dr Nepogodiev.

“We recommend that, whenever possible, surgery should be delayed for at least seven weeks after a positive Sars-CoV-2 test result, or until symptoms resolve if patients have ongoing symptoms for seven weeks or more after diagnosis.”

Dr Bhangu said: “Decisions regarding delaying surgery should be tailored for each patient, since the possible advantages of delaying surgery for at least seven weeks following Sars-CoV-2 diagnosis must be balanced against the potential risks of delay.

“For some urgent surgeries, for example for advanced tumours, surgeons and patients may decide that the risks of delay are not justified.”

Dr Mike Nathanson, president of the Association of Anaesthetists, said: “Of the millions of patients now waiting for surgery, many will have had Covid-19 and they will want to be informed about the risks.”

There are 15,000 co-authors of the paper, which is thought to be the largest collaborative surgery study ever undertaken globally.