Waikato is the latest area to roll out rapid antigen tests (RATs) as its laboratories struggle to meet Covid-19 testing demand.

The demand is causing a delay to process tests in the lab, with the DHB saying some tests may take up to seven days for a result.

Waikato District Health Board Covid-19 response executive lead Maree Munro says its labs are already at full capacity.

"We are seeing labs, reaching really, their full capacity and saying 'we can't deliver the results of tests in a timely manner, we need to do something about the demand that is coming in'."

As a result, Munro said it decided to use rapid antigen tests to combat demand.

Waikato is now the third region, behind Northland and Auckland, to have RATs available at community testing centres.

Munro says the use of rapid antigen testing, alongside PCR testing, will speed up the process as demand continues to grow through the Omicron outbreak.

There are 285 new cases of Covid-19 in Waikato on Tuesday, bringing the total to 1804 in the region.

Munro says while there is a level of anxiety in the community, there is a high demand of people who want a test but did not meet the criteria - ultimately holding up those who did meet criteria.

"If they're not symptomatic, then they shouldn't be coming.

"We are wanting to see those people who should be coming through the testing sites, not people who are asymptomatic and wanting the security of a negative result."

Munro says RATs will be rolled out to all testing centres in the city this week, but for now they were at the Founders Theatre and Greenwood testing centres.

A Covid-19 testing centre near Kaiaua on the Firth of Thames in September last year. Photo: RNZ / Andrew McRae.

The impact of the RATs did not appear to make an impact at Founders Theatre on Tuesday, as the line wound its way around two roundabouts.

Those in line were moving mere inches at a time and questioning if they had enough petrol for much needed aircon.

"I was told to come early and I was here early, but I've been here for three hours.

"Sitting in your car for three hours in this heat, you have no idea how bad it is."

Another person in the line said it was the news that RATs were available that motivated her to come.

"If we hadn't have known about that, we wouldn't have bothered to come and get tested.

"We would've just gone 'let's just wait and see what happens' but if we can have a RAT test we can get a result today."

However, others say despite the three-hour wait in a hot car, they would prefer a PCR test.

"For me personally, PCR is probably safer and faster so I would rather get that option than a RAT test," a person in line said.

"It's safer for everybody to [test] so we can move forward from this outbreak."

Testing nurses will determine what test a person will have based on a level of criteria set by the Ministry of Health.

-RNZ/Leah Tebbutt.