In-silico trials of targeted screening for abdominal aortic aneurysm using linked healthcare data

In this research we will look at the results of the NHS AAA Screening Programme since it began in 2013. General practice, hospital and mortality (death) records will be obtained for each man invited for screening using a process that ensures all men remain anonymous to the research team. By combining the results of AAA screening with this other NHS data, we will work out what would have happened if only men identified as smokers had been invited for AAA screening. This work will be extended to see if there are other risk factors in general practice records that can be used to identify men at high, or low risk of AAA. This information will be used to see if AAA screening can be targeted at groups of men who are at a high risk of having an AAA and, if so, whether such a targeted screening programme will still identify the majority of men with AAAs.

For this research we will use a process that ensures that the research team will not know the identity of the people involved in the research.

An abdominal aortic aneurysm (AAA) is a swelling of the main blood vessel in the body, the aorta. If an AAA gets too large it can burst (rupture) and cause dangerous internal bleeding. AAAs can be repaired by having an operation. Operations to repair an AAA once it has ruptured are much higher risk than operations done before an AAA ruptures. This means that most people diagnosed with an AAA are offered surgery to prevent rupture. In the UK around 8000 operations are performed to repair AAAs each year.

One of the main problems with AAAs is that they rarely cause any symptoms before they rupture. This means most patients will not know they have one. AAAs can easily be diagnosed with a simple ultrasound scan. It has been shown that offering an ultrasound scan to men to screen them for AAA can reduce the risk of dying from an AAA by half. All countries in the UK now offer AAA screening to all men in the year of their 65th birthday. Women are not offered screening because AAA is very uncommon in women.

In England, the NHS AAA Screening Programme (the NAAASP) is run by NHS England. The NAAASP invites about 280,000 men for AAA screening each year. Four out of 5 men attend for screening and about 1 in 100 men who are screened are found to have an AAA. 99 out of 100 men who attend for screening do not have an AAA.

Being invited for screening can cause people to worry about what the result of the test might be. Screening programmes are also expensive for the NHS. It would be beneficial if AAA screening could be targeted towards those men most likely to have an AAA. This would prevent people worrying about the result of a screening test unnecessarily. Any money saved could be used for other parts of the NHS.

One alternative approach to inviting all men for AAA screening is to only invite men for screening if they are at high risk of having an AAA. This approach is used in the United States where only those men who are current or ex-smokers are invited for AAA screening. This reduces the number of men who are screened. It is not known if this approach misses many men with AAAs from the group who are not offered screening.

This research will find out what would happen if AAA screening is only offered to men with known risk factors for AAA such as smoking. The number of men with AAAs who might be missed by a targeted screening programme will be assessed and compared with any benefits from reducing the overall screening programme size.

In this research screening results from the NAAASP will be combined with general practice records for each of the men who have been invited for screening. General practice records include information about an individual’s past medical history and smoking status amongst other information. By combining the results of AAA screening with general practice records what would have happened if only men identified as smokers had been invited for AAA screening can be worked out. This work can also be extended to see if there are other risk factors in general practice records that can be used to identify men at high, or low risk of AAA. This information will be used to see if AAA screening can be targeted at groups of men who are at a high risk of having an AAA and, if so, whether such a targeted screening programme would still identify all the men with AAAs.

This privacy notice has been published because this research will involve analysing screening results and other healthcare data from men who have previously been screened for AAA in the NAAASP. It is important that information about this work is made publicly available.

Two sources of data will be used:

1. The NAAASP records the outcomes for all men invited for AAA screening in a large database. Since the programme started over 2 million men have been invited for screening. When men are invited for screening, the NAAASP records whether they attended for screening or not. In those men who attend for screening the outcome of their screening scan is recorded.
2. The Clinical Practice Research Datalink (CPRD) is the national research database of general practice records. Not all GP records are included in CPRD, only those from practices where patients have been informed about CPRD. Patients under the care of these practices will have had the opportunity to opt-out of their data being used in CPRD. Data from CPRD are not routinely combined together with other data from the NHS or elsewhere.

Both NAAASP and CPRD of data are held by separate organizations and cannot be combined without special safeguards and permissions. Neither organization is currently allowed to hold both sets of data in a combined format for the purposes of medical research. To undertake this research special permission has been given by the NHS Health Research Authority Confidentiality Advisory Group (CAG) to join these datasets together (data linkage).

The CPRD has set up a process that allows their data and other external datasets to be joined together for research in a way that means the research team using the data cannot identify the people whose data it is. The way this is done is to use what is called a trusted third party. Previously this process used NHS Digital, the NHS’s digital information group, as a trusted third party. In January 2023 NHS Digital becomes part of NHS England who will now undertake this function.

Regulatory approvals

This linkage will be undertaken under the legal pathway of Section 251 approval from the NHS Health Research Authority Confidentiality Advisory Group (HRA CAG). This approval has been obtained by CPRD as part of the overall application to CPRD for non-standard linkages.

The above process does not require any personally identifiable information such as name, address or date of birth to be transferred or shared between any of the parties involved. The only identifier that is transferred between organizations is NHS number (from NAAASP and primary care system providers to NHS England). This will not be combined with any personal data such as medical records. NHS number on its own is not usually considered to be confidential information or personally identifiable information. NHS England already holds NHS numbers for all patients registered with a GP in England so no additional data sharing of NHS number will be taking place.

• NAAASP
• CPRD

If you don’t want your screening information or general practice records to be used in this way then you can opt out. You can either opt out of just this research project or all NHS research and data sharing. This will not affect the care you receive from the NHS. If you just want to opt out of this research project you can contact your local AAA screening unit. If you want to opt out of this and other NHS data sharing activities you can find out more information on how to do this at the NHS Choices website.

Approval for this research will be sought from several authorities.

The NHS England AAA Research, Innovation and Development Advisory Committee

This group approves all research that makes use of data from the NAAASP. This committee is made up of managers, doctors, lay members and public health experts from across England.

The Health Research Authority

This research involves the use of individual’s medical records without direct consent. This is undertaken under Section 251 of the Health and Social Care Act 2006. Approval for this work will have to be granted by the Health Research Authority Confidentiality Advisory Group. This research has also been approved by a Research Ethics Committee. These committees approve all medical research in the UK.