https://www.sciencedaily.com/releases/2022/10/221012194009.htm
"Cambridge scientists have shown that it is possible to spot signs of brain impairment in patients as early as nine years before they receive a diagnosis for one of a number of dementia-related diseases."
It's not a medical test (unfortunately) but rather an identification of a certain set of health and cognitive "markers" and therefore act as a screening for people "at risk".