A recent study has cast additional doubt on the cost-effectiveness of adding FDG-PET to the diagnostic workup of patients with suspected Alzheimer’s disease. The study found that using a contrast-enhanced MRI technique to confirm the results of clinical workup cost less and yielded more benefits than PET, while SPECT lagged both MRI and PET.
Based on the results of their analysis, the researchers concluded that although PET may have a high diagnostic accuracy for Alzheimer’s diagnosis, adding it to the standard diagnostic regimen at Alzheimer’s disease clinics would yield limited benefits at a very high cost.
In an article published in Radiology, authors Pamela McMahon and Dr. G. Scott Gazelle, Ph.D., of Massachusetts General Hospital in Boston evaluated the cost-effectiveness of FDG-PET in the diagnosis of Alzheimer’s in community-dwelling patients with mild or moderate dementia who present to specialized Alzheimer disease clinics. Their co-authors are from Harvard University in Cambridge, MA.
The researchers calculated the costs in the study by using 1999 dollars, adjusted for inflation, by using the medical care component of the U.S. consumer price index. Benefits of each exam course to the patient were expressed as gains in quality-adjusted life years (QALY) between 0 (death) and 1 (perfect health).
The team used the standard clinical workup for Alzheimer’s as its status quo for comparison.
"This includes acquisition of a detailed medical history, assessment of cognition and functional status, laboratory testing, and structural brain imaging with nonenhanced CT," the authors wrote (Radiology, August 2003, Vol. 228:27, pp. 515-522).
Next they analyzed the effects of different functional imaging additions to the standard clinical exam. These included computed SPECT, FDG-PET, or dynamic susceptibility-weighted contrast-enhanced MRI.
For each one of the imaging scenarios, the research group simulated 100,000 Monte Carlo trials, calculated the mean costs and mean effectiveness of each strategy, and determined incremental cost-effectiveness ratios. They used an 18-month time frame for the base-case analysis and health-related quality-of-life weights based on the Mark III version of the Health Utilities Index (HUI3).
The Health Utilities Index is a generic, preference-scored, comprehensive system for measuring health status, health-related quality of life, and producing scores that measure the utility of a particular therapy. It was developed by the Centre for Health Economics and Policy Analysis, McMaster University, Hamilton, Ontario, Canada.
The researchers found that "the addition of either PET or computed SPECT to the standard clinical examination results in a strategy that costs more but yields fewer gains in QALYs (Quality-Adjusted Life Years)."
For PET, they calculated a QALY of 0.7063 ±0.4127, compared with 0.7092 ±0.4120 for the standard clinical exam. For computed SPECT, the QALY was 0.7093 ±0.4137. Dynamic susceptibility-weighted contrast-enhanced MRI had a QALY of 0.7109 ±0.4110.
The cost of each of the strategies was calculated as $56,859 ±$18,569 for the standard clinical workup, $57,877 ±$18,927 for dynamic susceptibility-weighted contrast-enhanced MRI, $58,590 ±$18,799 for FDG-PET, and $58,872 ±$18,736 for computed SPECT.
The use of PET or computed SPECT was performed in a second visit only in those patients who received a diagnosis of possible or probable Alzheimer’s disease.
"In contrast, dynamic susceptibility-weighted contrast-enhanced MRI is an integrated structural and functional examination that can be performed instead of structural CT and thus was performed in all patients in that strategy, and patients were treated according to the results of this imaging examination," the researchers wrote.
They added that patients that have inconclusive standard examination results would receive the highest value from an accurate neuroimaging exam.
"In addition to enabling the initiation of therapy, an earlier diagnosis of Alzheimer’s disease would eliminate uncertainty and allow time to plan for caretaking, legal, and financial arrangements for the patient. Qualitative factors such as these are difficult to include in QALY measures, but they may be important considerations," they wrote.
By Jonathan S. BatchelorAuntMinnie.com staff writer
September 16, 2003
Related Reading
Scans suggest why education prevents Alzheimer’s, August 8, 2003
Alzheimer’s brains show features of immaturity, May 8, 2003
Imaging’s role still evolving in dementia diagnosis, April 29, 2003
PET reveals hippocampal role in preserving semantic memory, April 16, 2003
Using PET for Alzheimer's diagnosis lowers cost of care, October 21, 2002
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