How do we know whether or not a hospital is safe?

It is a question that has come to the fore amid fresh controversy over infections apparently contracted during treatment at the Queen Elizabeth University Hospital in Glasgow .

One key way of gauging safety is the Hospital Standardised Mortality Ratio (HSMR) , a scoring system designed to detect abnormally high death rates.

The tool was first devised by Professor Sir Brian Jarman in response to Bristol Royal Infirmary heart surgery scandal, where a “club culture” of insider and outsider clinicians was blamed for enabling unusually high mortality rates among its paediatric cardiology unit to go unchallenged for years despite repeated warnings from whistleblower Dr Stephen Bolsin.

HeraldScotland:

A inquiry concluded that 30 to 35 children who underwent heart surgery at the hospital between 1991 and 1995 would probably have survived if treated elsewhere.

Speaking in 2015, Sir Brian, a medical academic at Imperial College London who took part in the inquiry, said: “At the end I thought, it’s unacceptable that the mortality in the Bristol children’s heart unit was 30 per cent.

"The parents could have driven an hour away and gone to a hospital with a mortality of 6%–8%.

“We as a medical profession had an obligation to make that information available for these parents. So we started our unit. Our motto was that Bristol should never occur again.”

HSMR is now widely used worldwide, as well as in the UK and Scotland. It compares the actual number of deaths which occurred over a given period against the number which would have been expected based on statistical models which adjust for factors such as the age and co-morbidity of patients.

This produces a ‘score’ which is either above or below one where 1.05, for example, would indicate that mortality was 5% higher than predicted.

READ MORE: Sarwar takes aim at 'belligerent and complacent' health board over QEUH infections

These deaths were not necessarily avoidable - but if the figures are consistently and substantially higher than expected, it should trigger an investigation.

For example, Mid Staffordshire NHS Trust in England had an HSMR of 1.27 in 2005/6 and a subsequent public inquiry found that “appalling” standards of care, staff shortages and pressure to meet targets had contributed to hundreds of preventable patient deaths between 2005 and 2008.

HSMR is far from perfect, however.

Critics argue that it might flag problems which lie beyond the hospital - such as a comparatively low number of GPs per head in the local community - or that it may be skewed by the primary diagnosis on admission (for example, “chest pain”) as opposed to subsequent complications and actual cause of death.

HeraldScotland:

HeraldScotland: The QEUH had the lowest hospital standardised mortality ratio of any of NHS GGC's hospitals in the past year. It is shown as the orange dot to the rightThe QEUH had the lowest hospital standardised mortality ratio of any of NHS GGC's hospitals in the past year. It is shown as the orange dot to the right

Caveats aside, the HSMR for the Queen Elizabeth University Hospital has been consistently below one.

In the 12 months to June this year, its ratio was 0.92 - in other words, the actual number of deaths was 8% lower than expected based on the case mix of patients.

Vale of Leven and Inverclyde hospitals were both above one, though not significantly.

The QEUH’s rates of the three most common healthcare associated infections - E.coli, C.diff, and Staphylococcus aureus - are also not unusual.

READ MORE: Alarm raised over bacteria in water supply before QEUH opened

Yet trouble has dogged the facility from day one: testing before it opened in May 2015 detected “hygiene issues with the water supply” and the first known case of a child cancer patient developing a bloodstream infection, caused by rare water-borne bacteria Cupriavidus pauculus, occurred in February 2016

An independent review published in March this year concluded that, out of 109 infection episodes between 2015 and 2019 where Gram-negative environmental bacteria caused serious illness in children or teenagers being treated for cancer, leukaemia, and other blood diseases, 33 were “probably” related to the hospital environment and 76 “possibly” were.

Some infections resulted in intensive care admissions or delays to cancer treatment, and two deaths - including that of 10-year-old Milly Main - were “at least in part, the result of their infection”.

HeraldScotland: Louise Slorance (left) and Kimberley Darroch believe that details of infections which led, respectively, to their husband's and daughter's deaths at the QEUH were kept from themLouise Slorance (left) and Kimberley Darroch believe that details of infections which led, respectively, to their husband's and daughter's deaths at the QEUH were kept from them

In Milly’s case, it was “entirely possible” that a Stenotrophomonas infection “caused a critical further deterioration in heart function”.

To what extent the building’s water supply and ventilation systems have contributed to avoidable infections is the subject of an ongoing pubic inquiry.

As important though is an issue of culture: Milly Main’s mother, Kimberley Darroch, only discovered her daughter’s Stenotrophomonas when she saw it listed on her daughter’s death certificate, while Louise Slorance - whose husband Andrew, a Scottish Government official, was treated for lymphoma at the QEUH in late 2020 - only learned that he had also been treated prior to his death for aspergillosis, a fungal infection which can be deadly in immuno-compromised patients, after obtaining his medical records.

Given the question marks hanging over the QEUH, it is understandable that any lack of transparency would be interpreted as evidence of a “cover up”.

READ MORE: 'Whistleblowing destroyed out lives - more must be done to protect those to speak up'

For some ordinary staff on frontline, however, the infections saga has left them feeling under attack.

One QEUH nurse, who wrote to the Herald on condition of anonymity this week, said: “If [Scottish Labour leader Anas Sarwar] believes that the health board is covering up instances of infection, then he must believe that nurses are complicit in this, as we manage the care of our patients on a day to day basis and would be aware of infections that our patients contract.

"To say that we are being silenced by the health board is ridiculous and just not true.”

HeraldScotland: Drs Christine Peters (left) and Penelope ReddingDrs Christine Peters (left) and Penelope Redding

Yet others - including consultant microbiologists Dr Christine Peters and Dr Penelope Redding, now retired - have previously told the Herald they were “treated as troublemakers” for trying to flag concerns.

So is the QEUH safe? The statistics say yes - overall.

But have problems been missed, or ignored? Were patients and families left in the dark, and whistleblowers sometimes silenced?

If only we had an algorithm for that too.