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KCE Reports 82 Multislice CT in Coronary Heart Disease 83
Health
state
The quality of life values and their distributions for each of the states, on the basis of
which the QALY decrements are calculated are presented in Table 24.
Table 24: Distributions of quality of life index values used to calculate the
number of quality adjusted life days lost
Duration
of state
Quality of life
index values,
mean
Standard
deviation
Distribution Lower
bound
Baseline 0,86 0,16 Normal 0.2 1
PCI
procedure
1 month 0,69 0,2 Normal 0.25 1
CABG
procedure
1 month 0,68 0,2 Normal 0.25 1
CABG 2.5 0,78 0,17 Normal 0.5 1
follow-up months
Time horizon
Sensitivity analysis
Upper
bound
The impact of symptom relief from revascularisation on health-related quality of life was
not taken into account in our economic evaluation because it is questionable whether
the revascularisations performed in the study by Goldstein et al. actually induced pain
relief. They presumably were rather meant for diagnostic reasons, i.e. the prevention of
major cardiac events or death. While more revascularisations were performed during
the index hospitalisation in the MSCT-arm compared to the ”standard of care”-arm (5%
versus 1%), an equal number of patients were re-admitted for recurrent chest pain
during the 6 months follow-up period in both arms. 4 Hence, we can reasonable
conclude that the higher number of revascularisations did not reduce the risk of
recurrent chest pain.
The time horizon used in the economic model is the time horizon for which data are
available from the RCT, i.e. from admission to the emergency department up to 6
months follow-up. We assume that longer time horizons would not change the results
of the economic analysis, because it is uncertain whether the immediate CCAs and
consequent revascularisations performed in the 8 patients showing severe stenosis on
MSCT (over 70%) were clinically meaningful. As no MPS has been performed in these
patients it is impossible to draw conclusions about the clinical relevance of these CCAs
and revascularisations.
As for the outcomes, we assume that only invasive coronary procedures (CCA, PCI and
CABG) have an impact on the number QALYs. The absolute difference between the
number of QALYs in both procedures remains therefore de facto the same in extended
time periods if the difference in the number of invasive procedures remains the same.
Obviously, the relative impact of the quality of life loss due to the procedures decreases
if the time horizon increases.
Bootstrapping was performed to obtain confidence intervals around the cost and
outcome estimates in the economic evaluation. 1000 bootstrap samples were drawn
from the defined distributions. The distributions used in the bootstrapping for cost and
outcome variables are presented in the paragraphs where the sources and assumptions
with respect to the cost and outcome variables are discussed.
We verified the conclusions of Goldstein et al. by calculating the costs of both
diagnostic strategies up to the point where the decision to perform CCA is taken.
Costs of CCA or revascularisation were not included. 67 On the basis of this analysis,
Goldstein et al. concluded that the MSCT procedure is less costly than the standard of
care procedure. Outcomes, however, were not measured in terms of QALYs but in
terms of ”time to diagnosis”, which is, as explained earlier, not relevant for resource