What are Hospital Standardised Mortality Ratios?

Find out more about Hospital Standardised Mortality Ratios with Dr Foster Health

The Hospital Standardised Mortality Ratio (HSMR) is an indicator of healthcare quality that measures whether the death rate at a hospital is higher or lower than you would expect.

Like all statistics, HSMRs are not perfect. If a hospital has a high HSMR, it cannot be said for certain that this reflects failings in the care provided by the hospital. However, it can be a warning sign that things are going wrong.

Why are HSMRs important?

The Healthcare Commission (now the Care Quality Commission) recently criticised Mid-Staffordshire hospital for failings in the quality of care. They pointed out that the high hospital mortality rate at the hospital had provided strong evidence of the problems at the hospital.

On a more positive note, hospitals which have made efforts to improve the safety of the care have succeeded in reducing their HSMR.

How does HSMR work?

The HSMR compares the expected rate of death in a hospital with the actual rate of death. Dr Foster looks at those patients with diagnoses that most commonly result in death- for example, heart attacks, strokes or broken hips.

For each group of patients we can work out how often, on average, across the whole country, they survive their stay in hospital, and how often they die.

Dr Foster does this by taking into account their age, the severity of their illness and other factors, such as whether they live in a more or less deprived area. This allows us to work out how many patients we would expect to die at each hospital.

Dr Foster then compares this with the number of patients that actually die. If the two numbers are the same, the hospital gets a score of 100. If the number of dead is ten per cent less than expected they get a score of 90. If it is ten per cent higher than expected, they score 110.

How should HSMRs be interpreted?

Care is needed in interpreting these results. Just through chance, some hospitals will have a higher mortality rate and some a lower rate. It is inevitable that half the hospitals will have a worse than average result and that some will be quite a lot worse than the average.

Dr Foster particularly focuses on what we call "outliers". These are hospitals where the results lie outside the normal range.

On the Hospital Guide, for each hospital we show their result plus the range of results that might be expected from this hospital. It is only if the actual result is outside this range that we identify its results as higher or lower than expected.

If your hospital has a higher than expected HSMR, it is sensible to ask questions about why this is. You can ask your GP, your hospital doctor or the hospital Patient Advice and Liaison Service (PALS).

If you are concerned about the standards of care at your hospital you can complain to the PALS. Also, remember that in situations where it is not an emergency, you have the right to ask to be treated in a different hospital.

HSMR Case Studies - using HSMRs to improve patient care

Bradford Teaching Hospitals NHS Foundation Trust used mortality intelligence to trigger closer investigation of clinical care processes across medical and surgical specialties.

The trust began focusing on hospital mortality in 2002 when it joined the international programme Pursuing Perfection. The programme aimed to improve quality of care and required a commitment by senior managers and clinical staff in the hospital to eliminate all unnecessary hospital deaths.

The trust established a surveillance system to increase awareness and to review deaths. This included feedback summarising the routine collection of hospital data and certificates for each hospital death. The information was used to initiate an investigation of greater depth through a case-note audit.

To improve patient safety, the trust targeted the review of the prescription and administration of high risk medicines and also strengthened its infection control policy. For example, the trust ran a hand hygiene campaign and held staff awareness sessions.

As a result of these and other initiatives, HSMRs at the trust fell from 94.6 in 2001 to 77.5 in 2005. This translated to 905 fewer deaths than would have been expected between 2002 and 2005.

HSMRs in the news

The recent Healthcare Commission investigation into Mid Staffordshire Hospital NHS trust has brought HSMRs into the news once again.

The Commission noted that it was only after the publication of the 2007 Dr Foster Hospital Guide, where the trust was named as having a significantly high HSMR that the trust and the SHA took notice and began to investigate the problem.

The trust was criticised for assuming that data anomalies were causing the high rate when in fact the Healthcare Commission found failings in the quality of care. Indeed they conclude:

"Trusts [must] be able to get access to timely and reliable information on comparative mortality and other outcomes, conduct objective and robust reviews of mortality rates and individual cases, rather than assuming errors in data."

As a result, the government is publishing one-year HSMRs through NHS Choices from April 30 2009.

Where else can I see my local hospital's HSMR?

Dr Foster Health presents one-year, three-year and trend analysis data for HSMRs in English NHS acute hospitals.

In order to find out a hospital's HSMR for a particular medical procedure, go to the homepage and click on Hospital Guide on the top navigation bar.

Select the medical procedure you are interested in - Hip Replacement for example - type in your postcode and chose the distance you are willing to travel. Then click on the search button and a list of hospitals will appear.

Chose the hospital you want to investigate and click on the link to open the record page. In figure 1 below, you can see at the bottom of the page a list of indicators across the page: wait times; length of stay; infection control, etc.

The HSMR indicator is at the end of the tabbed list. Click on the HSMR tab to reveal either one-year, three-year or trend analysis graphs of HSMRs at the hospital you chose for Hip Replacement.

Figure 1: Three-year HSMR data (Hospital Guide)

If you see that HSMRs for this particular medical procedure are in the red (higher than expected), you might want to ask your consultant or GP why that might be so.

If you want to find out more about how HSMRs and how they are calculated, visit the Methodology Section on Dr Foster Health and scroll down to "Hospital Standardised Mortality Ratio 1 Year, 3 Years and Trend". Then click on the expand button to read the explanation.