Eligibility is based on need, measured by a range of criteria including a community services card, distance travelled, and a number of trips in a short period.
The NTA requires the distance travelled to be 80km or more, but the distance between Wanganui and Palmerston North is 78km. However, most people who travel between the two cities for treatment are already covered under the NTA due to frequency of travel and their community services cards.
If the 80km threshold was waived by the WDHB as a special circumstance, more people would be eligible for funding, and the cost to the DHB would be about $200,000 a year, depending on how many people took up the option.
"How do we find the people who actually have been complaining or are upset about it?" Ms McKinnon asked.
Board member Kate Joblin said the DHB needed to get a feel for the size of the need.
Chief executive Julie Paterson said they would "try to get a better handle on the extent".
"We still don't know if we've got a problem," she said.
Board member Judith MacDonald said the subsidised amount was "pitiful" and said the DHB - according to national policy - was only funding 28 cents per km travelled.
The IRD rate was 77 cents, she said. "Is it right to invest in the hospital when we should be giving back to the community?
"People being discharged from Wellington are told to find their own way back to Wanganui - is that okay? No, damn right that's not okay."
Some people were ineligible for support simply because they didn't fit in the right geographical area, she said.
Mrs MacDonald believed it was "not just a health issue".
Ms McKinnon said more research needed to be done, and Ms Paterson believed it was a social issue rather than a health one, but "you can better your bottom dollar nobody else will be putting their hand up".
"This is high priority for the board," she said.