Researchers have estimated about how much an after-hours GP clinic can take pressure off an overextended hospital emergency room.

A 10-year review of patient movements in the NSW of Wagga Wagga has introduced an after-hours GP clinic that had a welcoming impact on its hospital emergency department (ED).

The ED took care, on average, 7.04 fewer patients everyday who had injuries or illness that were described as low urgency after the clinic's opening in 2003.

The total number of patients who turned up at the ED dropped by 8 percent, guaranteeing medical staffers have more time to deal with patients who have higher-needs and are in emergency cases.

We found strong data of an association between the opening of the after-hours clinics and the decline in the presentation of low-urgency patients to the ED, said statistician Savid Buckley.

As people with less urgent health concerns go to see a GP, the hospital was able to cope with small rise in people with a more serious problem.

Over the period, there was an additional of 1.36 patients a day who went on to be rated as imminently life-threatening.

Mr Buckley said that the debate about the value of after-hours GP clinics offers are centered on their ability to ease access block or those patients who waited too long in an ED.

The effect of these after-hours clinics was examined in the perspective of their capability to reduce access block, where their value is considered often as limited, he said.

Mr Buckley's research is published in the latest edition of the Medical Journal of Australia.