The collaboration, led by Daniel Silverman at University of California, Los Angeles, used PET analysis to examine glucose metabolism in 284 patients who presented with mild cognitive impairment between 1991 and 1998. Two hundred ten patients were predicted by PET to have progressive dementia. This was subsequently confirmed in 91percent of cases either by a follow-up clinical evaluation conducted at least two years after PET scans (78 patients), or by a neuropathological examination (113 patients) performed, on average, 2.9 years after PET. The analysis also categorized 74 patients as being non-progressive and only 15 of these turned out to be false negatives. "PET, as demonstrated by this study, shows a specificity and sensitivity that makes it the premier imaging modality for diagnosis," said coauthor Mony de Leon at New York University School of Medicine.

In addition, diagnosis by PET removes some of the subjectivity associated with memory tests, which can be complicated by language difficulties or the patient's level of education. The study leaves unsolved the question of precisely how favorably PET diagnosis compares with diagnosis by an experienced neurologist, nor did it address the question of how early PET can predict future AD. But could PET improve monitoring of disease progression, or track the efficacy of potential treatments? "Absolutely," said de Leon.-Tom Fagan.

Reference:Silverman DH, Small GW, Chang CY, Lu CS, Kung De Aburto MA, Chen W, Czernin J, Rapoport SI, Pietrini P, Alexander GE, Schapiro MB, Jagust WJ, Hoffman JM, Welsh-Bohmer KA, Alavi A, Clark CM, Salmon E, de Leon MJ, Mielke R, Cummings JL, Kowell AP, Gambhir SS, Hoh CK, Phelps ME. Positron emission tomography in evaluation of dementia: Regional brain metabolism and long-term outcome. JAMA. 2001 Nov 7;286(17):2120-7. Abstract

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