When looking at classical hierarchies in scientific evidence (Fig. 1) as first described by the Canadian Task Force on the Periodic Health Examination [2], typically registries would appear as a “cohort study” in terms of the value of evi­dence that they provide—hence with more observer bias than randomised control trials (RCTs).

Registries are very distinct from clinical trials which are designed to test hypotheses and require power calculations to determine the appropriate number of cases that need to be recruited in order to show statistical differences. Registries are not bound by power calculations and in the ideal world are never ending par­ticularly because they can provide very useful trend data on patient demograph­ics, surgical practice and outcomes which can change quite dramatically even over relatively short periods of time. This is well illustrated in the series of IFSO Global Registry Reports, the last of which—the Fifth Report [3] which shows a rapid uptake in sleeve gastrectomy worldwide in over just a few years, with a dip in the number of Roux-en-Y cases, and a new upsurge in One Anastomosis Gastric Bypass procedures especially in certain countries.

Instead think of registries as helping to reset understanding about outcomes. They can report on real world practice instead of the best outcomes reported in the medical literature and can give surgeons confidence that they can compare their practice with others and share this information with patients.

Clinical Trials come to a natural end when the recruitment of patients and the collection of initial and follow up data has been completed and the data have been analysed, whereas registries can go on and probably should go on forever. Indeed, typically the functionality of high quality registries is that the inbuilt analysis capability can be extended and expanded over time. This is helped by the ever increasing speed of registry software development and innovation which leads to faster and more extensive reporting and analytic capability. The British National Bariatric and Metabolic Surgery Registry (NBSR) now offers instant dashboards and extensive one-button-push composite reports, neither of which could have been conceived of when the registry was first constructed. These reports have enhanced the functionality of the registry to provide surgeons with reports that can go straight into Appraisal files and can be created in seconds, whereas manually assembling the equivalent information even a year ago might have taken many days of effort for an individual surgeon to gather all the neces­sary data together. The real beauty is that registries can provide operational func­tionality that goes way beyond just addressing particular scientific questions, the real strength of registries is the capacity to provide a comprehensive suite of outputs:

obesity related diseases over time

– Revision surgery outcomes

• Dashboard analyses

Starting a National Registry is usually driven by either Specialist Societies wish­ing to provide a service to their surgical and patient community or by Ministries of Health and Governments wishing to monitor the performance of the bariatric service provision within a country.

The most successful registries are most often formed by specialist Surgical Societies. Why is this the case?

✓ Societies tend to have a long-lasting & uniform mission & “direction of travel”,

which can be independent of government policy which can change with each

over time

or even two years for such a post. The development of a registry is a long pro­cess and it is vital that there is careful stewardship of the process over an extended period of time. Some would recommend a tenure for a Database Chairman of a minimum of 5 years with the option to extend between a further 3 and 5 years. The danger of rolling the position every one or two years is that by the time the individual has worked out how to do the job, it is being handed straight over to the next person who has to go through the same learning curve to get up to speed to manage the project—this roll-over process leads to too many “stops & starts” and can put a long term registry project at huge risk of failure.

When seeking to identify and recruit an individual to take on the role of Database Chairman there are a number of key attributes that are highly desirable. Namely the person should:

Just in the same way that writing the objectives or mission statement for a surgi­cal society or association is a necessary challenge, doing the same for a surgical registry is also an essential but not easy task. Indeed the two are often interlinked. Setting up a Surgical Society involves creating a constitution and key roles and responsibilities for both Executive Council members and for members of the Society. Setting up a registry also requires constitutional considerations, decid­ing who can sit on the Database Committee, how long the tenure should be, what determines quorate decisions and so on.

Writing down the objectives is so critically important as these then drive the dataset design and reporting requirements along with steering the required activi­ties of the Committee and its chosen data management partner. The objectives may start off very simply indeed and may centre around feasibility of enrolling all cen­tres within a country and demonstrating that basic data can be merged, analysed and reported. Down-the-road, second tier objectives are likely to be included, such as providing benchmarks of activity and performance. The objectives of a Registry should ideally be reviewed on an annual basis and should include sign-off from a Society Executive Board.

The International Federation for the Surgery of Obesity and Metabolic Disorders is proposing a full Delphi study to review existing datasets and to ensure that data col­lection is designed not just to track surgical outcomes, but also to consider patient per­spectives and input from all stakeholders involved in bariatric and metabolic medicine and surgery. Likewise, there are attempts underway to develop a Patient Recorded Outcome Measure (PROM) that is very specific and tailored to obesity management.

Union laws [6] on data protection and privacy. Every registry must now have in place not just a designated data controller but also the right documentation and processes around data management and patient confidentiality. For properly anonymised registries that are better described as “audit”, consent is not a require­ment, but it is nevertheless generally “advised” and indeed is mandatory if a national registry is collecting identifiable personal data.

It is essential that any partnering data management company that is acting as the Registry “Data Processor” can demonstrate compliance with the highest levels of data security.

It might be tempting to think that bariatric surgery registries are primarily for sur­geons. In reality there are multiple other stakeholders who take a deep interest in the analyses and the reported outcomes coming from a registry including:

There will always be a group of surgeons who are the innovators followed closely by early adopters. Fairly rapidly there will be an adoption swell of early majority and late majority users followed finally by the laggards who are reticent to adopt new technology unless they are forced to join, become too embarrassed by not taking part or just simply wait until they can see everybody else regards the project as a real success and being involved can no longer be avoided.

There is constant discussion at surgical Scientific Congresses about who should shoulder the responsibility of Data Collection. Some will say that the data col­lector should be completely independent of the clinical team (in order to elimi­nate bias), often a North American viewpoint, whereas in other cultures e.g. the British environment there is a different mantra, namely: “The operation is not fin­ished when you, or your assistant, puts the last stitch into the patient, the operation is finished when the data has been entered into a database”. Professor Sir Bruce Keogh (former Medical Director of NHS England) in his introduction to the 1st UK National Bariatric Surgery Report [8] stated: “After all, in my view, if you can’t describe what you’re doing and define how well you’re doing it, you have no right to be doing it at all”.

It is an absolute imperative to ensure that registries do not become data cemeteries where data are never seen again. In order to encourage continued data collection and the success of any registry, regular outputs must be generated. These should span:

NHS Bariatric Surgery [9]