The usefulness of amyloid imaging in predicting the clinical outcome after two years in subjects with mild cognitive impairment.

BACKGROUND

Mild cognitive impairment (MCI) is a syndrome heterogeneous with regards to etiology and prognosis. Amyloid imaging enables to visualize a hallmark pathology of Alzheimer's disease (AD). Therefore we aimed to assess the usefulness of [(11)C]PiB PET for predicting clinical outcome of MCI patients after an interval of 2 years.

METHODS

In 28 MCI participants with a global CDR rating at baseline of 0.5 a baseline examination including clinical assessments and [(11)C]PiB PET imaging and a clinical follow-up examination after a planned interval of 24 months were performed. Predictive values and accuracy of amyloid-positive and negative scans for conversion to dementia of any type and to dementia due to AD were calculated and compared to neuropsychological tests and ApoE genotyping.

RESULTS

Of 17 MCI patients who were amyloid-positive at baseline converted 9 to dementia all of the AD type. 3 of the 11 amyloid-negative MCI subjects converted to dementia but none to dementia due to AD. PPV, NPV and accuracy (to dementia: 0.53, 0.73 and 0.61; to AD: 0.53, 1.00 and 0.70) was comparable to neuropsychological tests and superior to ApoE genotyping.

CONCLUSION

All MCI subjects who converted to dementia due to AD were amyloid-positive. However, only 50% of these MCI due to AD, intermediate likelihood, patients developed manifest dementia due to AD after 24 months limiting the usefulness of [(11)C]PiB PET for individual prediction of clinical outcome.