Molecular tests able to predict up to 83 per cent of future Alzheimer's cases in individuals with mild cognitive impairment have been developed by Swedish scientists.
However, until at-risk patients can be given treatment to modify the disease, such tests are not appropriate for routine use, the researchers warned.
The tests measure cerebrospinal fluid levels of beta-amyloid-42, total tau protein and P-tau.
The researchers measured levels of the markers in 750 individuals with mild cognitive impairment, 529 with Alzheimer's disease and 304 controls. Participants were spread across 12 research centres.
Individuals with mild cognitive impairment were then followed until they were cognitively stable for two years or were diagnosed with Alzheimer's.
Alzheimer's was diagnosed in 271 of the 750 individuals with mild cognitive impairment at the start of the study.
Using the three molecular markers, the researchers were able to predict the development of Alzheimer's with a sensitivity of 83 per cent and specificity of 88 per cent.
The researchers suggest that, without appropriate treatment, the tests may be primarily useful as a screening tool for selecting individuals for more detailed further clinical follow-up or in clinical trials.
The authors of an accompanying editorial agree that the tests will have limited use in practice until new treatments are available.
'Alzheimer's disease has no treatment to prevent or alter the course of the disease, so making the diagnosis with good accuracy may aid in planning but also could be devastating news for some patients and families,' they said.