A report that found there was no statistical relationship between discharges from hospital and covid-19 outbreaks in Scottish care homes has been revised to suggest a link ‘cannot’ be ruled out.

Public Health Scotland says the strongest predictor of an outbreak at a care home remains the number of residents it had, with largest homes the worst affected.

The discharge of large numbers of often older adults from hospitals to care homes in the early days of the pandemic has proved controversial because most discharges took place before testing was in place.

Nearly 3,000 of the 3,599 patients discharged in March and early April 2020 did not receive a test for coronavirus.

In the revised report published today, Public Health Scotland repeats its original conclusion: ‘No statistically significant association was found between hospital discharge and the occurrence of a care home outbreak.”

But it adds: ‘However, due to the uncertainty observed, we cannot rule out a small effect, particularly for those patients who were discharged untested or discharged positive.

‘Care home size is much more strongly associated with the risk of an outbreak than other care home characteristics, including the different types (negative test, untested, positive test) of hospital discharge.’

Changes to the analysis followed an intervention by a UK statistics watchdog.

In January, Ed Humpherson of the Office for Statistics Regulation wrote to Public Health Scotland saying sections of the report could be confusing to readers and that sections of the report gave too little weight to the ‘uncertainty’ inherent in interpreting the data.

Nearly a third of the 1,084 care homes in Scotland recorded a virus outbreak between 1 March and 21 June, with 1,915 covid-related deaths across 321 care facilities.

The chance of an outbreak increased progressively as the number of residents in a home did, Public Health Scotland said, with just 3.7% of homes with fewer than 20 beds reporting an outbreak compared to 90.2% of those with 90 or more registered places.

Read more: Covid care home discharge report ‘not the full story’; Fewer than 5 covid care home transfers at NHS board; Delayed discharge failure allowed virus ‘catastrophe’

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