Trusts placed into special measures last year for persistently high mortality rates have shown signs of improvement, a report by three healthcare bodies has found.

The report by the Care Quality Commission, Monitor and the NHS Trust Development Authority shows that fewer of the 11 so-called Keogh trusts are now “outliers” in two mortality measures, compared with the period before NHS England medical director Sir Bruce Keogh launched his review in February last year.

Sir Bruce was tasked by the prime minister with inspecting 14 trusts with persistently high mortality rates, 11 of which were subsequently put in special measures.

According to last week’s joint report, it was “too early to make definitive statements” about mortality rates at the trusts because of a lag in data coming through, and the need to compare improvements at the 11 trusts with progress nationally.

However, the report added that the latest data showed there had been “some improvement across the trusts examined”.

This view was echoed by two experts in health statistics.

Sir Brian Jarman, a co-director of Dr Foster Unit at Imperial College who helped develop the hospital standardised mortality ratio indicator, said: “Eyeballing the data, it does look to me as if it’s going in the right direction.”

However, he added: “We don’t actually rebase the data for the year ending in March until roughly November… [so] we can’t at the moment say they are definitely better or not.”

Veena Raleigh, senior fellow at the King’s Fund, said “some trusts do seem to show an improvement between their Keogh report and the inspection by the CQC”, which she described as “encouraging”.

However, she said mortality rates should be used with caution.

“We know that all these indicators can’t be seen in isolation, so the fact that some have a high mortality rate doesn’t necessarily mean they’re providing poor quality care.

“Equally, some that don’t appear to have a high mortality rate, unless other things have been checked it’s no guarantee that they do provide a good quality of care.

“A mortality rate… cannot be ignored [but] I think in a perfect world it would be more informative to be considering in greater detail mortality rates that are condition specific or procedure specific because they’re just sharper.”