A team of medical researchers has found that the 2,500-year-old Pythagoras theorem could be the most effective way to identify the point at which a patient's health begins to improve.
According to the theorem, in a right-angled triangle, the sum of the squares of the two right-angled sides is equal to the square of it's hypotenuse.
In other words, one can determine the length of the hypotenuse given the length of the other two sides.
For many chronic conditions, epidemiologists agree that the correct point to choose is that which is closest to the top-left corner of the plot containing the curve.
"As we stopped to think about it, it struck us as obvious that the way to choose this point was by using Pythagoras theorem," explained Rob Froud from Warwick Medical School at University of Warwick, Britain.
Froud and his colleague Gary Abel from University of Cambridge made the discovery after looking at data from ROC (Receiver Operating Characteristic) curves.
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These curves were initially developed during World War II for the analysis of signals to help operators decide if a blip on the screen was an enemy target or allied forces ships or aircraft.
Later, in the 1980s, these curves were adopted by epidemiologists to help them decide at what point an individual has recovered from an illness.
They set about exploring the implications of this and how it might change conclusions in research.
"We conducted several experiments using real trial data and it seems using Pythagoras' theorem makes a material difference. It helps to identify the point at which a patient has improved with more consistency and accuracy than other methods commonly used," Froud pointed out.
The moral of the story is that before you throw out the old stuff in the attic - just go through it one last time - as there may be something in there that is still relevant and useful, the team concluded.
The study appeared in the journal Plos One.