Speaking on behalf of the departing general practices, he said patients from these practices could be assured that it was "business as usual" as far as their core medical services were concerned.
"Their high-quality medical services remain unchanged."
He had heard of patients worrying unnecessarily that they would not be able to get medication or laboratory tests.
The majority of patients did not necessarily come in contact with extra services provided by Well Dunedin such as the free interpretation service or under-25 sexual health checks, he said.
There would be patient information going into practices and advertisements in the Otago Daily Times and community newspapers soon about the changes, he said.
Patients who might be concerned about not being able to access any of the special programmes provided through Well Dunedin had the choice to leave a departing practice and enrol in another one.
Prof Tilyard said, however, he had "never heard of anyone changing practice because of a change in PHO".
Last weekend, Well Dunedin took out a half-page advertisement entitled "Changes to GP Services" outlining extra services it funded and inviting patients to telephone staff for further information about how practices moving might affect their access to services.
Well Dunedin chief executive Sandy Baines said advertisements had been low key and designed to inform patients about how the move might potentially affect them.
Approval for the transfer of the practices has been given by the Otago District Health Board, but Ms Baines will be raising concerns with the board about the way this has been handled.
Thursday's Otago Daily Times omitted Meridian Medical Centre from its list of practices departing to Taieri and Strath Taieri PHO.
There are 12 health centres, incorporating 13 practices, making the move.
