My wife took the Addenbrooke's test in May 2016, scored 91 and was diagnosed with MCI. In May 2017 she was retested and scored 88 with other tests showing various problems and was diagnosed with Possible Early Onset Dementia of uncertain Aetiology. A PET scan in Oct, 2017 showed brain shrinkage in 2 areas that was in addition to vascular damage that was visible on earlier CT and MRI scans and a diagnosis of Alzheimer's was made. At a consultation in late Oct, 2017 the Consultant said he did not test further as it would just be cruel.
The point about cruelty in a moot one as the first score and diagnosis of MCI led my wife and me to do a lot of research and we discovered that not all cases of MCI develop into dementia and, indeed, when underlying depression and/or anxiety are treated scores can revert to normal. This led my wife to live in hope and me to live in a state of some bewilderment as I could see her deteriorating. The diagnosis of possible dementia and then Alzheimer's then hit my wife very hard indeed, although maybe that would be the case anyway.