A sign of good psychomotor skills
Doctors at some of the UK's busiest music festivals say a young patient's ability to use a mobile may be a good test of how ill they are.
Each year hundreds of festivalgoers who have either fainted or suffered panic attacks are treated in medical tents.
Medical teams noticed that as soon as they were well enough to text their friends, they were generally well enough to rejoin the action.
The test could work in busy A&E units, they told the British Medical Journal.
Some of the UK's best known festivals are supplied with doctors, nurses, paramedics and first aiders by Festival Medical Services, a charitable trust.
However, during certain performances, their three-metre square tents can be some of the busiest on the site - and in the face of dozens of "casualties", most of whom were recovering from fainting while in the crowd, doctors needed to find a way to work out who needed further attention, and who could be discharged.
Dr Mike Sinclair, a retired anaesthetist who has worked for Festival Medical Services for 25 years, said: "It started during a performance by Green Day at Reading in 2004 - we were inundated with people.
Medics treated 142 people during a Bloc Party set at Reading
"Then we noticed that as soon as they could, teenagers would pull out their mobile phones and start texting their friends, telling them what had happened and arranging where to meet.
"At that point we realised that they must be well enough, provided they had no other injuries, to be released."
The "psychomotor co-ordination" needed to text required the brain to be working at a reasonable level, he said.
"Obviously, we did not check to make sure the texts made sense - but this might not be easy, given that many of them appear to make no sense at the best of times."
In subsequent years, the "text test" was applied more actively in busy times, allowing them to treat 142 patients in under an hour during a Bloc Party performance at Reading this year, and a similar number over 90 minutes during a Rage Against the Machine set at the same festival.
Dr Sinclair suggested that it might even have a place in a busy hospital A&E department.
However, Jim Bethel, a lecturer in emergency care and nurse practitioner at a Walsall A&E department, was not entirely convinced.
"I can't imagine it would be a criteria for discharge in an A&E setting, but it could certainly make you less concerned than you otherwise might be about a particular patient."
However, he said: "The present way of assessing consciousness - the Glasgow Coma Score - is quite cumbersome to apply."