Conversion of amyloid positive and negative MCI to AD over 3 years: an 11C-PIB PET study.
BACKGROUND
Patients with amnestic mild cognitive impairment (MCI) represent an important clinical group as they are at increased risk of developing Alzheimer disease (AD). (11)C-PIB PET is an in vivo marker of brain amyloid load.


OBJECTIVE
To assess the rates of conversion of MCI to AD during a 3-year follow-up period and to compare levels of amyloid deposition between MCI converters and nonconverters.


METHODS
Thirty-one subjects with MCI with baseline (11)C-PIB PET, MRI, and neuropsychometry have been clinically followed up for 1 to 3 years (2.68 +/- 0.6 years). Raised cortical (11)C-PIB binding in subjects with MCI was detected with region of interest analysis and statistical parametric mapping.


RESULTS
Seventeen of 31 (55%) subjects with MCI had increased (11)C-PIB retention at baseline and 14 of these 17 (82%) clinically converted to AD during follow-up. Only one of the 14 PIB-negative MCI cases converted to AD. Of the PIB-positive subjects with MCI, half (47%) converted to AD within 1 year of baseline PIB PET, these faster converters having higher tracer-retention values than slower converters in the anterior cingulate (p = 0.027) and frontal cortex (p = 0.031). Seven of 17 (41%) subjects with MCI with known APOE status were epsilon4 allele carriers, this genotype being associated with faster conversion rates in PIB-positive subjects with MCI (p = 0.035).


CONCLUSIONS
PIB-positive subjects with mild cognitive impairment (MCI) are significantly more likely to convert to AD than PIB-negative patients, faster converters having higher PIB retention levels at baseline than slower converters. In vivo detection of amyloid deposition in MCI with PIB PET provides useful prognostic information.
Okello
A
A
Division of Neuroscience and Mental Health, Faculty of Medicine, Imperial College London, UK.
Koivunen
J
J
Edison
P
P
Archer
H A
HA
Turkheimer
F E
FE
Någren
K
K
Bullock
R
R
Walker
Z
Z
Kennedy
A
A
Fox
N C
NC
Rossor
M N
MN
Rinne
J O
JO
Brooks
D J
DJ
D000368:Aged; D000544:Alzheimer Disease / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D000647:Amnesia / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology; D000814:Aniline Compounds; D002250:Carbon Radioisotopes; D003072:Cognition Disorders / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D058225:Plaque, Amyloid / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D049268:Positron-Emission Tomography / Q000379:methods*; D013844:Thiazoles; D013997:Time Factors
C475519:2-(4'-(methylamino)phenyl)-6-hydroxybenzothiazole; D000814:Aniline Compounds; D002250:Carbon Radioisotopes; D013844:Thiazoles