Symptomless NSW residents have been urged to reconsider going to COVID-19 testing clinics as a pre-Christmas surge causes delays.

Clinics at Stanmore and the international airport in Sydney turned people away on Tuesday morning despite some waiting three hours.

“It’s just frustrating,” Mitchell Jones, who went to both clinics before giving up, told AAP.

“I wanted to be safe as I’m needing to see elderly family in Newcastle over Christmas.

“I had run out of RATs (rapid antigen tests), and figured they were like gold now.”

Meanwhile, extreme demand at Northern Beaches Hospital’s drive-in testing clinic stopped hospital staff getting to work and led the management to stop testing asymptomatic people unless they were close contacts or needed to be swabbed for work.

“Please be kind to our staff – they’re doing their very best in this time of high activity, as well as having some colleagues absent from work due to being community close contacts,” hospital chief executive Andrew Newton said on Monday.

NSW pathology labs have processed more than 700,000 tests since Wednesday evening, with more than 12,800 coming back positive.

The long queues have also caused trouble for positive cases.

Sydney student Guy, who asked his surname not be published, says he spent an hour in a long queue at the Prince of Wales Hospital clinic in Randwick on Saturday before giving up.

Come Sunday, he tried another clinic but was denied the opportunity to skip the one-hour queue when telling staff he felt ill and had returned multiple positive RATs.

“You can’t stand the heat when you’re sick,” he told AAP.

The 21-year-old, whose clinic test done on Sunday came back positive on Tuesday, would like to see more shelter provided for those sweltering in the summer heat.

“If you’re immunocompromised or elderly, that’s just a bit crappy situation to be in,” he said.

Chief Health Officer Kerry Chant said it was important to reduce testing of asymptomatic people so higher-value cases, such as people with symptoms, could be prioritised.

“We do encourage people to use rapid antigen testing, particularly if you want to have that piece of mind before going out to a social event … or going to be mixing with vulnerable or elderly people,” she said on Tuesday.

More than 450 COVID-19 testing locations are open across NSW, many of which are open seven days a week.

– AAP