Analysis: Making GP data count

Extraction of GP data could make a huge contribution to medical research, but will it be at the expense of confidentiality? Stephen Robinson reports.

Within weeks, patient data will be extracted from GP practice systems on an unprecedented scale., the controversial data extraction scheme led by NHS England, will begin mining information on disease diagnosis, prescriptions, vaccination status and more from the health records of millions of patients across England.

Practices are mandated by the Health and Social Care Act 2012 to provide their anonymised data, but some fear that patients could still be identified. Recently, GPs have also raised concerns that they have not had enough time to inform patients about the new scheme, potentially putting practices in a difficult legal position as data controllers.

But while makes headlines, another GP data extraction service quietly gathering momentum could have a huge impact on global medical research.

Data success

The Clinical Practice Research Datalink (CPRD) is the successor to the General Practice Research Database, first launched in 1987. The comprehensive database contains clinical data from more than 5m patients at more than 600 GP practices in the UK.

Control was passed to the DH in 1994, before being handed to the MHRA in 1997. It became the CPRD in April 2012 and has been backed by £60m joint funding between the MHRA and the National Institute for Health Research.

CPRD director John Parkinson PhD has worked with the system since 2007 and says GP data can help answer fundamental questions in medical research. 'There's no doubt about it, GP data is absolutely fabulous for research,' he says.

What is the Clinical Practice Research Datalink?
  • CPRD extracts anonymised patient information from participating practices' computer systems to provide data for research studies.
  • Data includes medical diagnoses, referrals, secondary care treatment, prescriptions, lifestyle information and more.
  • Data can be linked to other datasets on acute care episodes, mortality and genetics.
  • Researchers, academic or commercial, can apply to access datasets for research projects.
  • Researchers must be contracted to CPRD and projects approved by the Independent Scientific Advisory Committee.


Linking datasets

The power of CPRD is that it links data from 50 named datasets across the NHS and public health; everything from acute hospital episodes to genetic data. It promises to give researchers the information needed to improve clinical care, public health and the safety of medicines.

CPRD is now actively recruiting GP practices to join up, starting with an attempt to sign up 2,500 practices already taking part in clinical research via the Primary Care Research Network.

Dr Parkinson says a larger dataset allows researchers more easily and effectively to investigate the big medical questions on a grand scale.

The types of research it permits include a new generation of pragmatic clinical trials - investigating best practice alongside routine care.

Pilots of pragmatic clinical trials are already under way. These use CPRD software to direct clinical treatment in real time.

One trial aims to determine if patients with acute exacerbation of COPD but with non-purulent sputum should be prescribed antibiotics. If both GP and patient agree to take part in the trial, software randomises patients to receive antibiotics or not when presenting with the condition.

The software then watches for future GP codes indicating a repeat visit, prescription or hospital attendance, and logs the outcome of that intervention. It is hoped that when data from thousands of such consultations are combined, the findings can help improve the treatment provided in general practice.

Dr Parkinson says: 'It's cost-efficient, done with normal prescriptions. We are almost the only country in the world that can run these studies because of the NHS and powerful, well-coded systems.'

Data access

Access to potentially millions of patients' data gives researchers a powerful tool to explore care for rarer conditions too.

Researchers using CPRD data are currently investigating the effect of anti-epileptics taken in pregnancy, so that the safest treatments can be found. Dr Parkinson explains: 'We need the data from as many pregnancies as possible, because the issues around drugs in pregnancy are quite rare. But it's the rarity of them that means we need data from as many pregnant women as possible, which means we need access to as many practices as possible.'

Monitoring side-effects and effectiveness of treatments in the real world, in real time, will be key to determining drug safety in future.

Nowhere is that needed more than where a drug is used off-label in children. Dr Parkinson says: 'It's out of the GP primary care records that we can say, look at this body of learning, which then comes to the regulator, goes back to the company, and then there can be a more official policy on how to manage children.'

Data privacy is paramount for practices as data controllers. But with so much data leaving the surgery, can practices be assured it is safe?

CPRD insists its systems are secure. Data is extracted from GP IT systems via a push system: practices retain control of the data flow, with a 'kill switch' allowing them instantly to turn off the feed at any time.

Data is anonymised before it is extracted by CPRD. Applications to use the data can be made by researchers working for commercial or public organisations, including pharmaceutical companies. But a strict governance and approval structure ensures only vetted researchers and organisations are given access, with tough security measures to prevent misuse of the data.

'We make data available to a very wide range of researchers, not always in this country. They are academic, NHS and commercial researchers,' says Dr Parkinson.

'Every piece of research is done under a legal agreement. We've been operating now for over 20 years. As far as I'm aware, there has never been a problem with any of our releases of data, both in the UK and elsewhere.

'One area that we all have to be very, very careful of, is the more data you have the more, potentially, it is disclosive.'

He says researchers are prevented from analysing information in subgroups smaller than five patients, which he says is 'fundamental' to ensuring anonymised data remain that way.

'We think every line of data, every piece of data - doesn't matter whether it's linked or not - deserves to have the same level of privacy and confidentiality applied to it.

'Am I complacent? No, because I'm the guy that will ultimately be hit if anything did go wrong. We are always reviewing what we do.'


The BMA and the RCGP support the system, which is also compliant with standards in the Caldicott 2 information governance review.

Northumberland LMC secretary Dr Jane Lothian has spoken out against the mandatory data collection in, saying NHS England's eight-week window to inform patients is not long enough. She believes practices risk legal challenges if patients are identified.

But she says the opt-in model for CPRD gives practices time to alert patients before data is released. 'There's an extra level of governance. Plus, research projects have to be approved, so there's extra assurance.'

Glasgow GP Dr Peter Wiggins has provided data to CPRD since 1989 and says it 'exceeds his expectations' over data security.

Aside from contributing to medical research, practices could also see direct benefits in their surgery. Dr Wiggins says the scheme has improved the standard of data recording in his practice, allowing it to 'walk straight into' fundholding when it arrived.

Even practices joining now will 'reap big benefits'. Above all, the system allows practices to contribute to research that could improve the care they provide. Dr Parkinson says: 'Not all GPs want to be researchers. But every GP practice can enable research by putting data into the pot.

'If you see health research like the ultimate jigsaw - the 10m-piece jigsaw - it may be you can't find that last piece. It may well be that those series of practices we've not got in at the moment may just hold that piece of the jigsaw.'

What GPs should tell patients

NHS England, working with the BMA and the RCGP, has produced a poster and leaflet that practices can display to inform patients about the plans to send their data outside the practice walls. This covers as well as the CPRD scheme.

Although permission from patients to extract anonymised data is not legally required, CPRD allows patients to opt out if they choose.

But CPRD director John Parkinson says opt-out rates have been extremely low. 'The history of that is only 1,000 patients out of 12m have decided to take that route.

'Most patients are happy with it. If you ask them the question, do you want drug safety research to go on, do you want to know the drugs in everyday use are effective, do you want to know that patients who are pregnant can take this drug, do you want to help children with rare diseases, people say yes, but I want to know the data is being used properly.'

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