Only a small minority of cases of long Covid are being recorded by GPs, a study has suggested.

Previous research estimated that as many as two million people in England are suffering ongoing symptoms after a Covid-19 infection.

A new study has found that only 23,273 cases were formally recorded between February 2020 and April 2021 at GP practices.

Experts analysed data from GP records of 57.9 million patients in England – about 96% of GP patients across the nation.

More than a quarter of practices (26.7%) had never logged a case, according to the article in the British Journal of General Practice.

Experts from Oxford University and the London School of Hygiene and Tropical Medicine said the study raised questions about how long Covid is diagnosed, recorded and managed in the NHS.

The outgoing chief of the NHS in England has made significant pledges to help patients suffering ongoing symptoms after an infection.

Sir Simon Stevens previously said long Covid is “one of the major health challenges emerging from the pandemic”.

Services set up so far include an online rehabilitation support system, specialist hubs for children and young people, and a network of specialist long Covid clinics for adults.

But the new findings raise questions over how people can be referred to the services if their cases have not been logged.

The lead researcher of the study, Dr Ben Goldacre from the University of Oxford, told the PA news agency: “People have recently been publishing on prevalence of long Covid, and they have reported very high figures – the React 2 study reported that approximately two million people have the condition.

“We looked at what is recorded in patients’ notes. And we were able to look at the pseudonymised records of 58 million patients – that is an unprecedented scale of data access.

“What we found in there, for long Covid, was almost unbelievably different to the survey data – it’s almost a 100-fold difference.

“So the React 2 study said approximately two million people may have long Covid, we found that only 23,000 patients had ever been recorded as having the condition until April 2021.

“So there is an enormous difference in the extent to which people are having this diagnosed formally on the record compared with people’s self-reports of their medical problems in survey data.”

Academics suggested there could be a number of reasons for the findings, including patients not yet seeing a GP about symptoms, doctors having different diagnostic thresholds or criteria, and issues around how the diagnosis is recorded in GP computer systems.

Symptoms of long Covid can include shortness of breath and extreme fatigue, with almost a third of sufferers saying it has a significant impact on their daily life.

For some people it is highly debilitating.

It has been found to occur in people of all ages – including children – regardless of the severity of their initial illness.