SPECT perfusion imaging in the diagnosis of Alzheimer's disease - A clinical-pathologic study

Objective: Numerous studies have suggested that temporoparietal hypoperfusi on seen on brain imaging with SPECT may be useful in diagnosing AD during l ife. However, these studies have often been limited by lack of pathologic v alidation and unrepresentative samples. The authors performed this study to determine whether SPECT imaging provides diagnostically useful information in addition to that obtained from a clinical examination. Methods: Clinica l data and SPECT images were collected prospectively, and patients were fol lowed to autopsy. Clinical history, pathologic findings, and SPECT images w ere each evaluated by raters blind to other features, and clinical and SPEC T diagnoses were compared with pathologic diagnoses. The study population c onsisted of 70 patients with dementia, followed to autopsy; 14 controls fol lowed to autopsy; and 71 controls (no autopsy performed). The primary outco me was the likelihood of a pathologic diagnosis of AD given a positive clin ical diagnosis, a positive SPECT diagnosis, and bath. Results: When all par ticipants (patients and controls) were included in the analysis, the clinic al diagnosis of "probable" AD was associated with an 84% likelihood of path ologic AD. A positive SPECT scan raised the likelihood of AD to 92%, wherea s a negative SPECT scan lowered the likelihood to 70%. SPECT was more usefu l when the clinical diagnosis was "possible" AD, with the likelihood of 67% without SPECT, 84% with a positive SPECT, and 52% with a negative SPECT. S imilar results were found when only patients with dementia were included in the analysis. Conclusions: In the evaluation of dementia, SPECT imaging ca n provide clinically useful information indicating the presence of AD in ad dition to the information that is obtained from clinical evaluation.