"It's not possible to incentivise everything. It [bonuses] does improve quality in the short to medium term but it has a small detrimental effect on activities that do not attract financial targets," Dr Tim Doran, a clinical research fellow at Manchester University told the Daily Mail.
Other measurements that don't lead to extra bonus money includes measuring thyroid functions or blood sugar levels in certain patients. But a wide range of other measurements, including smoking habits and blood pressure, do attract bonus cash - and consequently better results.
But Doran thinks these results can also be difficult to measure. Especially when you attempt to measure conditions like depression. Previous research also found that targets designed to improve high blood pressure and cut heart attacks and strokes had little or no impact.
Social injustice?Meanwhile the government is reforming the structure of how GPs are paid, though with not much help from the British Medical Association (BMA); it's calling for the government's Health and Social Care Bill to be scrapped.
"Privatisation has been covertly going on under the radar for more than 10 years in the health service. We must never forget that private companies work on profit, not need," BMA member Dr Jacqueline Applebee told the media.
"If this bill is passed, the government will be administering one of the biggest social injustices placed on the British people."