At present, when someone calls 111, they are asked by an operator if they need police, fire or ambulance. If the caller chooses an ambulance, the y are put through to another operator who deals with the call.
Under the new system, that operator would code the call and send all those coded green, or least urgent, to the on-duty nurse.
The nurse will decide whether to make an appointment with the caller's GP, send a paramedic, or if necessary, an ambulance.
Company chairman Dr Martin Seers said the ProCare/Pegasus company Homecare Medical had stationed two or three nurses in the Auckland 111 call centre since last July.
St John communications head Victoria Hawkins said the trial avoided ambulance callouts for non-urgent conditions such as constipation, cramp, boils, piles, gout, sleeping problems, earache, toothache, backache and vomiting.
In the 11 months since the trial started, St John received 117,574 emergency calls in Auckland; 22,150 (18.8 per cent) were referred to nurses.
"This has freed up an extra 1.5 ambulances on the road 24 hours a day, seven days a week in Auckland."
Ms Hawkins said the trial would now be evaluated by an independent party by October, but in the meantime would be extended to support Northland and Waikato over the next three months.
Dr Seers said he hoped it would be rolled out nationally over the next few years.
"My understanding is that Wellington Free Ambulance are happy to work with us if we win the contract. We have also talked to the southern call centre," he said.
Meanwhile the new national helplines contract starts on November 1.
Dr Seers said the firm would seek access to parts of patients' health records so that helpline nurses answering calls in the middle of the night could understand the likely causes of callers' symptoms.
"The view would be that such a record will be available to a nurse doing a triage of someone who is acutely unwell so that she could say, 'Your doctor has you down as having emphysema', or 'I can see that you took a course of antibiotics two weeks ago', or 'You had a chest x-ray three months ago'."
Dr Kate Baddock, who chairs the Medical Association's General Practitioner Council, said GPs would give "cautious support" to sharing their patient records with Homecare Medical, which already operates the after-hours service for most Auckland GPs, as long as privacy and confidentiality issues could be managed.
The company is to keep all existing specialist helpline phone numbers but is also exploring a three-digit number similar to 111 for all non-urgent health calls.
Dr Seers said it was recruiting about 100 staff for the main healthline part of the new service for call centres in Auckland, Wellington and Christchurch. It would keep existing staff at the National Poisons Centre in Dunedin and was likely to hire many of the 59 staff at the Quitline stop-smoking service in Wellington and 15 at the alcohol and drug helpline in Christchurch.
The trial with the ambulance service became controversial last year after a TV3 staffer with a heart condition collapsed at work and had to wait an hour and 21 minutes for an ambulance. St John operations manager Michael Brooke said at the time the call should not have been coded green. The service made a mistake.