We all know that our body has an "internal clock" which determines when various daily biological processes take place. Problems can occur, however, if that clock is out of sync with the actual time of day. A simple new blood test can reportedly determine if that's the case, so that the situation can be addressed.

Our internal biological clock directs our body's circadian rhythm, which in turn determines things like our sleep-wake cycle. Should that clock be significantly misaligned with the time of day, possible consequences can include sleep and mood disorders, heart problems, diabetes and cognitive decline.

While it is already possible to determine how in-sync a person's biological clock is, doing so involves taking blood samples once an hour over a course of multiple hours. By contrast, the new TimeSignature test requires just two blood draws, taken at any time within a one-day period.

It was developed by scientists at Chicago's Northwestern University, who started by analyzing blood samples taken from a group of healthy test subjects once every two hours throughout the day. The researchers discovered that levels of 40 different gene expression markers were consistently higher or lower in those samples, at specific times. They then proceeded to create a machine-learning-based algorithm that could correctly calculate the time of day at which a sample was drawn, based on the concentration of those markers.

In the TimeSignature test, a patient's levels of those gene expression markers are compared to what they should be for the times of day at which the blood samples were taken. By doing so, it's possible to gauge the accuracy of that person's internal clock to within 1.5 hours. If it's significantly misaligned, steps can be taken to correct the problem. Additionally, if the patient is being put on medication that should be taken at a specific point in their circadian rhythm, the test will indicate what time of day that is.

"This is a much more precise and sophisticated measurement than identifying whether you are a morning lark or an night owl," says assistant professor Rosemary Braun, lead author of the study. "Various groups have tried to get at internal circadian time from a blood test, but nothing has been as accurate or as easy to use as TimeSignature."

The university has filed a patent on the technology, although it's also being made freely available to other institutions that wish to use it. A paper on the research was recently published in the journal PNAS.