A simple spit test could help predict when you're going to die, a new study on life expectancy suggests.
Researchers from the University of Birmingham studied 639 adults over a period of 19 years.
They discovered that there's an antibody in human saliva called immunoglobin A (IgA), which decreases more the closer a person gets to death.
Scientists believe the specific antibody could also be used as an efficient way to measure general health.
"There are a number of factors that can affect how well we produce antibodies and maintain their levels," Dr Anna Phillips from the University of Birmingham told the Mail Online.
"There are some that we have no control over, such as age, heritability or illness, but our general state of health can also affect their levels; stress, diet, exercise, alcohol and smoking can all influence those levels."
She added that they are unsure how saliva samples could be used in general health check-ups, as they need to "better understand what secretion rate would be considered cause for concern".
"We could certainly say that, if found to be extremely low, it would be a useful early indicator of risk," she explained.
The research was published in the journal PLOS One.
It's not the first study to use saliva tests as a way of predicting health. Other studies suggest spit tests could be used to predict the likelihood of a person developing Alzheimer's disease as well as certain cancers.