Principal component analysis of FDG PET in amnestic MCI.
OBJECTIVE
The purpose of the study is to evaluate the combined accuracy of episodic memory performance and (18)F-FDG PET in identifying patients with amnestic mild cognitive impairment (aMCI) converting to Alzheimer's disease (AD), aMCI non-converters, and controls.


METHODS
Thirty-three patients with aMCI and 15 controls (CTR) were followed up for a mean of 21 months. Eleven patients developed AD (MCI/AD) and 22 remained with aMCI (MCI/MCI). (18)F-FDG PET volumetric regions of interest underwent principal component analysis (PCA) that identified 12 principal components (PC), expressed by coarse component scores (CCS). Discriminant analysis was performed using the significant PCs and episodic memory scores.


RESULTS
PCA highlighted relative hypometabolism in PC5, including bilateral posterior cingulate and left temporal pole, and in PC7, including the bilateral orbitofrontal cortex, both in MCI/MCI and MCI/AD vs CTR. PC5 itself plus PC12, including the left lateral frontal cortex (LFC: BAs 44, 45, 46, 47), were significantly different between MCI/AD and MCI/MCI. By a three-group discriminant analysis, CTR were more accurately identified by PET-CCS + delayed recall score (100%), MCI/MCI by PET-CCS + either immediate or delayed recall scores (91%), while MCI/AD was identified by PET-CCS alone (82%). PET increased by 25% the correct allocations achieved by memory scores, while memory scores increased by 15% the correct allocations achieved by PET.


CONCLUSIONS
Combining memory performance and (18)F-FDG PET yielded a higher accuracy than each single tool in identifying CTR and MCI/MCI. The PC containing bilateral posterior cingulate and left temporal pole was the hallmark of MCI/MCI patients, while the PC including the left LFC was the hallmark of conversion to AD.
Nobili
Flavio
F
Clinical Neurophysiology, Department of Endocrinological and Medical Sciences, University of Genoa, Genoa, Italy. flaviomariano.nobili@hsanmartino.it
Salmaso
Dario
D
Morbelli
Silvia
S
Girtler
Nicola
N
Piccardo
Arnoldo
A
Brugnolo
Andrea
A
Dessi
Barbara
B
Larsson
Stig A
SA
Rodriguez
Guido
G
Pagani
Marco
M
D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis; D000647:Amnesia / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D016022:Case-Control Studies; D016002:Discriminant Analysis; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008568:Memory; D049268:Positron-Emission Tomography; D025341:Principal Component Analysis; D012680:Sensitivity and Specificity
D019788:Fluorodeoxyglucose F18