People under extreme stress have higher levels of cortisol, which is released by the body to suppress inflammation.
In comparison, those not under incredible stress can have no measurable levels of the hormone in their body by the evening.
Scientists at the Medical University of Vienna trialled their new saliva test on 66 volunteers, of which 40 had burnout.
They compared the work-related stress – derived from questionnaires - and cortisol levels between the two groups.
Previous saliva tests have tried to analyse cortisol levels in the morning, when the hormone is naturally produced.
The new method took swabs of saliva from the participants between 11.30am and 12.30pm and straight before going to bed.
It was found people experiencing burnout had noticeably higher cortisol levels at both time intervals.
Upon further analysis of the samples, the researchers were able to spot almost all of the volunteers who had burnout.
Their study, published in Scientific Reports, backed up previous evidence that early morning samples were not as accurate.
Some of the patients who were identified as being at risk of burn out using the new test were treated in a special stress clinic.
Writing in the journal, researchers said: 'This means that we can use these markers for preventively identifying people who are at greater risk of burnout.'
However, the researchers, led by a team of three, have now called for further trials to confirm the accuracy of the swabs of saliva.
What is burnout?
As many as one in three workers are estimated to become victims of burnout at some time in their career.
Even celebrities are not immune, as Kendall Jenner, Lady Gaga, Rita Ora and Ellie Goulding have all been struck in the past.
It also can lead to physical effects such as insomnia and headaches, while the prolonged stress raises the risks of heart disease.
