In December of 2001, the Duke Evidence Practice Center (EPC) completed a technology assessment to review the existing scientific evidence with regard to the role of 2-Fluoro 2-deoxy D-glucose Positron Emission Tomography (FDG-PET) in assisting with the diagnosis of early dementia in elderly patients for whom the differential diagnosis included one or more kinds of neurodegenerative disease. There were two main conclusions 1) PET improves the overall accuracy of diagnosis compared to accuracy of an examination based on American Academy of Neurology (AAN) guidelines and 2) treatment based on a standard AAN-recommended examination leads to better health outcomes than treatment based on PET results. This result was robust to a broad range of assumptions. Based on the assumption that new data may have been published since 2000 that may impact these original findings, CMS requested an update of the technology assessment.
In order to identify literature that would clarify the role of FDG-PET for use in these patients, a revised review was conducted to address three separate areas in which PET might be useful: diagnosis, prognosis and response to therapy. Twenty-two studies were initially identified for abstract review. Based on a review of these studies, including references and input from experts, four studies were identified for full text review. One examined the use of PET in distinguishing Parkinsonian dementia from AD (Bohnen, 2003). Three other studies described the ability of FDG-PET to predict progression to AD in patients with mild cognitive impairment (Chetelat, 2003; Arnaiz 2001; Silverman 2003).
Of the four studies identified for full text review, one examined the use of PET in distinguishing Parkinsonian dementia from AD (Bohnen, 2003). The three other studies described the ability of FDG-PET to predict progression to AD in patients with mild cognitive impairment (Chetelat, 2003; Arnaiz 2001; Silverman 2003).
Based on a review of these articles, there are two conclusions. 1) Publications since the prior TA do not provide evidence supporting revised estimates of the operating characteristics of PET for discriminating AD from other competing diagnoses. 2) Three studies suggest FDG-PET could be valuable for distinguishing patients with MCI who rapidly convert to frank AD. Two were relatively small studies that require validation and assessment of incremental value above conventional clinical measures. A third, larger study of FDG PET for prediction of progression for patients with MCI also suggests a potential role for PET in predicting clinical course for patients with dementia. However, this study did not comment on findings for patients with AD only, and results for PET, while suggestive of higher sensitivity and specificity, did not differ in a statistically significant manner from clinical findings.
In addition, CMS requested that the Duke EPC review and summarize in the form of an annotated bibliography, the existing scientific evidence with regard to the role of single-photon emission CT (SPECT), volumetric assessment by computed tomography or magnetic resonance imaging (Volumetric CT/MRI), functional magnetic resonance imaging (fMRI), and magnetic resonance spectroscopy (MRS) in the diagnosis, prognosis and estimates of responsiveness to treatment for patients with cognitive abnormalities. Of 472 articles initially identified for abstract review, 12 articles for SPECT, 9 for Volumetric CT/MRI, 2 for fMRI, and 4 for MRS eventually met all inclusion criteria and are summarized as an annotated bibliography.