Patients whose care sees GPs receive financial payments are being prioritised at the expense of others, research suggests.

A new study found quality of care improved at a much higher rate for conditions where payments were made to GPs than for those where no reward was offered.

Experts analysed electronic patient data from 1999 onwards from 148 GP practices in England, covering more than 650,000 patients.

They looked at 23 indicators included in the Quality and Outcomes Framework, a scheme whereby GP practices receive financial incentives for monitoring conditions such as heart disease, high blood pressure and diabetes.

This data was compared with 19 indicators not included in the QOF, including for people with arthritis, dementia and back pain.

The results showed that quality of care was improving for all indicators before the QOF was introduced in 2004.

But after incentives were brought in, the indicators included in the QOF performed much better than was predicted.

Improvement rates for indicators not included in QOF were “significantly below” what was expected.

The authors, from the universities of Oxford, Manchester and Bristol, said: “Improvements associated with financial incentives seem to have been achieved at the expense of small detrimental effects on aspects of care that were not incentivised.”

They said the findings raise important questions about the potential unintended consequences of financial incentive schemes.

“With ‘pay for performance’ schemes there is a risk that rewarding performance of certain clinical activities will divert attention from other, unrewarded activities,” they wrote.

QOF links up to a quarter of UK general practitioner income to performance on several indicators, costing the NHS about £1bn a year in England.

The latest research showed that, for incentivised activities, quality of care improved significantly in the first year of the scheme, but quickly reached a plateau in the second and third years of the scheme.

Nevertheless, quality of care in 2006-07 remained higher than predicted before 2004.

For non-incentivised activities, there was no overall effect on the rate of improvement in the first year of the scheme.

However, by the third year of the scheme quality was significantly worse than projected from pre-incentive trends.

A Department of Health spokeswoman said: “GPs should always provide care for patients based on clinical need, not on financial rewards. While the current system has delivered some important improvements in quality of care, this clearly shows that it needs to change and focus more on patients.

“The plans we have proposed in the Health and Social Care Bill focus on the quality of patient care.

“Clinical commissioning groups will have a legal duty to support the NHS Commissioning Board in continuously improving the quality of patient care and will be accountable for the health outcomes they achieve for all their patients.”