J Nucl Med 2002 Feb;43(2):253-66
Evaluating early dementia with and without assessment of regional cerebral
metabolism by PET: a comparison of predicted costs and benefits.
Silverman DH, Gambhir SS, Huang HW, Schwimmer J, Kim S, Small GW, Chodosh J,
Czernin J, Phelps ME.
Evaluating dementia in patients with early symptoms of cognitive decline is
clinically challenging. Growing evidence indicates that appropriate
incorporation of PET into the clinical work-up can improve diagnostic and
prognostic accuracy with respect to Alzheimer's disease (AD), the most common
cause of dementia in the geriatric population. The precise diagnostic role of
PET and its economic impact in this context, however, have not been
systematically examined previously. METHODS: We compared the relative value of 2
strategies for assessing whether early AD is responsible for cognitive symptoms
in geriatric patients: (a) a conventional approach, based largely on
establishing clinical criteria for the presence of dementia and excluding non-AD
etiologies that could contribute to the patient's symptoms, and (b) a proposed
approach using PET to examine regional cerebral metabolism and look for
characteristic patterns of abnormal metabolism. The total costs (measured in
dollars) and benefits (measured in number of accurate diagnoses) of diagnostic
testing and clinical outcomes accruing to each strategy were calculated using
formalized tools of decision analysis. The primary outcome measure by which the
strategies were compared was the ratio of costs to benefits obtained following
each approach. RESULTS: Following the proposed approach led to improved accuracy
in identifying early AD, without adding to the overall costs of diagnosis and
treatment ($3,433 vs. $3,564 per patient approached by the proposed or
conventional algorithm, respectively). The strategy making use of PET was
associated with a reduced rate of false-negative and false-positive findings
compared with the conventional approach (3.1% vs. 8.2% and 12.0% vs. 23.0%,
respectively, at a prevalence of 51.6% in the studied symptomatic population)
and a cost savings of $1,138 per correct diagnosis rendered ($4,047 vs. $5,185).
The lower cost per unit benefit for the proposed strategy was maintained over a
wide range of tested values for variables of sensitivity, specificity, costs of
PET and long-term care, and varying approaches to the use of structural
neuroimaging. CONCLUSION: Appropriate use of PET for evaluating early dementia
in geriatric patients can add valuable information to the clinical work-up,
without adding to the overall costs of evaluation and management, resulting in a
greater number of patients being accurately diagnosed for the same level of
financial expenditure. Thus, the opportunity exists for diminishing the
morbidity of dementia economically, with earlier institution of more appropriate
management in evaluated patients.
