Air New Zealand wants health authorities to consider Covid-19 saliva tests for surveillance monitoring of its crew who now face repeated and uncomfortable nasal swabs.
Some crew faced close to 20 nasopharyngeal swab tests a month in this country and overseas which were invasive and uncomfortable.
Saliva tests for Covid are being increasingly used overseas after studies have found accuracy rates similar to the nasal swabs.
Air New Zealand's chief medical officer Dr Ben Johnston said the Ministry of Health "was aware" of the airline's interest in saliva testing for its crew.
Two new studies out this month have found saliva testing — which requires someone to spit into a receptacle that is then sent for analysis — can be as accurate as nasal swabs.
A Yale School of Public Health study led by Kiwi scientist Dr Anne Wyllie has found saliva samples may even detect the virus better than a nasal swab.
The SalivaDirect test has been granted emergency use authorisation by the US Food and Drug Administration.
Not only is it easier, it removes about 80 to 90 per cent of the cost.
Johnston said health care workers had to wear personal protective equipment and have close contact with the donor.
"We understand that surveillance testing of asymptomatic workers is likely to be required for some time and for those workers who are being tested frequently it's really important to make those tests as simple and easy and as comfortable as possible."
Saliva tests were used for Air NZ crew when they arrived at Hong Kong but those going there - and to Shanghai and Samoa - needed a negative nasal swab before departing.
The ministry currently requires mandatory testing for crew who had returned from the "high risk" layovers in the US — Los Angeles and San Francisco, No Air NZ crew had tested positive after any flight since April 6, Johnston said.
"I'm talking daily with air crew who have had lots of tests and a number of them are getting quite anxious about a test — they find it unpleasant," he said.
"If saliva testing can be validated for use in New Zealand that removes a lot from the testing process. It would also potentially remove the need for a donor to come to a testing station because they could produce the sample themselves into a receptacle that has been provided and then drop that off somewhere."
Comment has been sought from the ministry whose current advice to health workers is to take a throat swab if a nasopharyngeal swab can't be tolerated.
Johnston said he understood saliva testing could be complicated by the greater care needed for the handling and analysis of the sample.
The ministry doesn't require testing for domestic crew but many have had tests voluntarily following flights for returnees or by those with cold or flu symptoms.
He said air crew would be an ideal study group for saliva testing.
''Anything that is simpler and faster is good for the wider population, so sending that out to border workers, health care workers and any group that requires surveillance testing. It would remain to be seen whether saliva testing would meet the standards of diagnostic testing - I could see there might be a difference there.''
Johnston said the chances of catching Covid while flying was low. There had been just a handful of cases internationally but a study being done with the ministry showed that of 264 passengers later found to have Covid since March, none had passed it on to crew which also made transmission to fellow flyers unlikely too.
The use of masks reduced risks even further and now they were mandatory that made it clear cut for airlines.
The saliva tests
The Yale research has been reported in the New England Journal of Medicine and the researchers point out the collection of saliva samples by patients themselves negates the need for direct interaction between health care workers and patients.
''This interaction is a source of major testing bottlenecks and presents a risk of nosocomial infection. Collection of saliva samples by patients themselves also alleviates demands for supplies of swabs and personal protective equipment.''
The saliva tests did a better job of detecting Covid. In the first five days after diagnosis, 81 per cent of the saliva tests came back positive, compared with 71 per cent the nasal tests. A similar gap remained through the 10 days after diagnosis.
The researchers detected more copies of the virus' genetic material in patients' saliva than in nasal samples.
SalivaDirect, is being further validated as a test for asymptomatic people through a programme that tests players and staff from the National Basketball Association (NBA).
A Yale pathology professor has said it could double daily testing capacity.
New Zealand's Science Media Centre asked experts here to comment on the research.
Dr Nikki Freed, senior lecturer in the School of Natural and Computational Sciences, Massey University said the study was very promising.
''While still preliminary and not yet peer-reviewed, the work shows that saliva may be better than nasopharyngeal swabs. From my perspective, saliva has a lot of advantages over nasopharyngeal swabbing, namely that it is easy to self administer and non-invasive. Most people can easily spit in a cup.''
Dr Freed is researching rapid diagnosis and genome sequencing to follow the coronavirus outbreak.
Professor David Murdoch, dean and head of campus at the University of Otago in Christchurch, said collection of the best possible sample was critical for any diagnostic test. A test result can be misleading if the sample tested has not been collected in the right manner or is of the wrong type.
"The saliva samples were collected by asking patients to repeatedly spit into a sterile urine cup until roughly a third full of liquid. The results of the study indicated that saliva performed as well as nasopharyngeal swabs at detecting cases of Covid-19, and indeed performed slightly better,'' he said.
"The authors offer a word of caution in noting that their study only included patients who had moderate or severe disease and that the findings may be different when testing people with mild or asymptomatic disease.''