Earlier this month, the first set of data on post-operative patient reported outcome measures (PROMs) was published by the Department of Health. For the first time, this has provided a patient-based assessment of changes in patients’ health-related quality of life following hip replacement. The data also cover surgery on knees, varicose veins, and groin hernias.

Between April 2009 and April 2010, more than 14,000 patients who had had hip surgery from more than 200 English NHS and private hospitals completed PROMs questionnaires both before and after surgery. Data are still being collected and will soon build up to one of the world’s largest sets of PROMs information. While the Department emphasises that the figures are “experimental” – released to encourage comment, debate, and suggestions for improvement –  the initial headline figures are fascinating.

So, which hospital is best at hips?

We have looked at the EQ-5D, which provides a patient’s rating of their own health in response to five key questions. This is then summarised as an overall index score and adjusted to take account of differences in each trust’s case mix.  It turns out that Whipps Cross Hospital has the largest improvement in patient-reported health, though when case mix is taken into account the overall winner is Mid Essex Hospital Services NHS Trust. The difference between the best and worst performers is large – a 49 per cent improvement versus 31 per cent – although the numbers of patients aren’t yet big enough for us to identify statistically significant differences. Data on other hospitals are available.

Just to be clear; these data don’t measure patients’ experience of their care or their satisfaction with it; rather they measure outcomes in terms of patients’ own assessments of their pain, mobility, mental state, and ability to function normally. They offer evidence about health outcomes at a level of detail never before seen in the NHS, which fits well with the Transparency in Outcomes framework outlined in the recent health White Paper.

As well as comparing how much hospitals improve health, what else is gained from measuring PROMs?

Putting PROMs and data on hospitals’ costs together, we can begin to look at how cost effectively hospitals are improving their patients’ health. Using a simple model, we have estimated how much, on average, it costs hospitals to generate one quality-adjusted life year (QALY) by carrying out hip replacements.

Like the PROMs data, our results are also “experimental”: it’s possible to use more sophisticated methods to measure hospital efficiency, and research is under way to apply those methods to PROMs data. However, even a simple analysis is revealing. Together with Professor David Parkin, Chief Economist, South East Coast SHA, Nancy Devlin and I have analysed the PROMs data on hip operations, and it suggests that hip replacements are very cost effective – around £1,000 per QALY gained. That compares very well to NICE’s threshold range of £20,000 to £30,000. But cost effectiveness seems to vary considerably between hospitals, and the differences appear to be statistically significant. And further, these seem to be driven as much by differences in costs as variations in outcomes.

All of this raises important questions for the NHS as it tackles its productivity challenge. How can some hospitals achieve better outcomes for the same cost? Could high-cost hospitals reduce costs without affecting outcomes?  The initial PROMs data suggest that there is much to be learned from hospitals that achieve good outcomes in a cost-effective way.

Find out more with our publication: Getting the most out of PROMS

John Appleby is the chief economist at The King’s Fund, and Nancy Devlin is the director of research at the Office of Health Economics, which receives funding from the ABPI. She is an elected member of the Executive of the EuroQol Group, a not-for-profit organisation which developed the EQ-5D.This blog also appears on the King’s Fund website