Table 1.
Compared strategies.
Figure 1.
Decision tree for an individual tested for Alzheimer's disease (AD).
Possible outcomes of the testing procedure are depicted as a function of the individual's health status for: (a) The primary scenario (testing of over-70 patients consulting for dementia symptoms). (b) The “screen and treat” scenario (systematic screening of the over-60 population). Depending on the investigated strategy, the generic “diagnostic test” mentioned in the trees may be standard diagnosis, standard MRI or MRI+CLP. When AD is diagnosed, the imaging procedures are followed by a cognition test (MMSE) in order to determine the disease stage. No test is performed in severe AD patients, who are assumed to be diagnosed directly.
Table 2.
Results of the primary analysis (base-case hypothesis): computed cost, efficacy and cost-effectiveness (C/E) ratio of the standard diagnosis, standard MRI and MRI+CLP strategies, and incremental cost-effectiveness ratios (ICER) of the MRI+CLP strategy as compared with the standard MRI strategy.
Table 3.
Partial rank correlation coefficients (PRCC) between input values and the ICER of the MRI+CLP strategy (compared with the preferred strategy).
Figure 2.
Results of the primary analysis: multivariate sensitivity analysis.
The strategy with maximum net monetary benefit is depicted as a function of the assumed sensitivity and specificity of the MRI+CLP diagnostic test, for assumed costs of the CLP contrast agent between 0 and 500€ per injection (in the absence of treatment T): (a) Cost of the CLP contrast agent at 50 €/injection. (b) Cost of the CLP contrast agent at 250 €/injection. (c) Cost of the CLP contrast agent over 450 €/injection.
Table 4.
Results of the “screen and treat” analyses (base-case hypothesis): computed cost, efficacy and cost-effectiveness (C/E) ratio of the standard diagnosis, standard MRI and MRI+CLP strategies, and incremental cost-effectiveness ratio (ICER) of the MRI+CLP strategy as compared with the standard MRI strategy.
Figure 3.
Results of the “screen and treat” (population-wide screening) analysis: multivariate sensitivity analysis.
The strategy with maximum net monetary benefit is depicted as a function of the assumed efficacy and cost of the hypothetical new drug T, for assumed specificities of the MRI+CLP diagnosis test between 0.80 and 0.99. The efficacy of treatment T is expressed as a 0-to-1 ratio between assumed probabilities of transition from early stage AD with and without treatment T; 0 corresponds to maximum efficacy and 1 to no efficacy (in the base case, fT = 0.5: 50% reduction). Only costs lower than the base-case cost of 500€ per 6-month treatment are investigated here. (a) specificity for MRI+CLP inferior to 0.97 (including base case). (b) 0.98 specificity for MRI+CLP. (c) 0.99 specificity for MRI+CLP.
Figure 4.
Results of the “screen and treat” (population-wide screening) analysis: multivariate sensitivity analysis.
The strategy with maximum net monetary benefit is depicted as a function of the assumed prevalence of AD in the general over-60 population (between 0 and 10%) and specificity of the MRI+CLP diagnostic test between 0.90 and 1, for assumed costs of the CLP contrast agent between 0 and 500€ per injection: (a) Cost of the CLP contrast agent at 50 €/injection. (b) Cost of the CLP contrast agent at 250 €/injection (base-case). (c) Cost of the CLP contrast agent at 500 €/injection.