Leiner_edit.qxp 28/7/08 12:40 pm Page 54
Imaging Magnetic Resonance Angiography
Figure 2: Sensitivity Analysis of Values for the Probability of a
compared with ECCM changes when the probability of bypass
Bypass in Critical Limb Ischaemia
following gadofosveset-enhanced MRA is lower than about 0.07 and
that following ECCM-enhanced MRA is higher than 0.10. The
0.36
sensitivity analyses on the correlation between the probabilities of
GF-MRA
PTA with gadofosveset and with ECCM are shown in Figure 5. Here,
0.34
ECCM-MRA
the advantage changes in favour of conventional ECCM when the
probability of PTA following gadofosveset-enhanced MRA is lower
0.32
than 0.57 and the corresponding probability following ECCM-
0.30
enhanced MRA is higher than 0.60.
0.28
The effect of diagnostic confidence was also analysed for IC from
Probability of bypass (ECCM)
the payer and hospital perspectives. With regard to base case I, from the
0.26 payer perspective no advantage of gadofosveset-enhanced MRA
over ECCM-enhanced MRA was found when the diagnostic confidence of
0.24
ECCM-enhanced MRA was set higher than 0.85 (see Figure 6). Considering
0.18 0.20 0.22 0.24 0.26 0.28 0.30
the comparison between the diagnostic confidence following gadofosveset-
Probability of bypass (GF)
enhanced MRA and standard DSA from a payer perspective (base case I), no
advantage of gadofosveset-enhanced MRA over DSA was found when the
Results of the two-way sensitivity analysis of the probabilities of bypass after initial gadofosveset (GF)-enhanced
magnetic resonance angiography (MRA) and after initial extracellular contrast medium (ECCM)-enhanced MRA for
diagnostic confidence of the MRA is below 0.85. For base case II, ECCM-
critical limb ischaemia patients (payer perspective, base case I). The area in question shows the initial diagnosis
enhanced MRA was found to be a more advantageous option compared
technique that gave the lowest cost per quality-adjusted life-year (QALY). Initial standard digital subtraction
angiography (DSA) was included in the comparison, but it is not shown, as it never gave the lowest cost per QALY. with gadofosveset when the diagnostic confidence with ECCM-enhanced
MRA is above 0.83 and that with gadofosveset-enhanced MRA is lower than
Figure 3: Sensitivity Analysis of Values for the Probability of
Threat of Amputation in Critical Limb Ischaemia
0.94. The sensitivity analyses for diagnostic confidence of gadofosveset-
enhanced MRA compared with ECCM-enhanced MRA and standard DSA
from a hospital perspective show that the results of the model are robust for
GF-MRA
0.15
a diagnostic confidence of more than 0.68 with gadofosveset-enhanced
MRA in base case I. For base case II, the results of the model were sensitive
ECCM-MRA
to variations in diagnostic confidence. Here, gadofosveset-enhanced MRA
0.14
was mostly dominated by conventional ECCM-enhanced MRA.
0.13
Discussion
In 2008, Ouwendijk et al.
32
published an economic evaluation of the cost
0.12 and effects of MRA in the diagnostic work-up of the lower extremities. They
compared Doppler ultrasonography, MRA and CT angiography (CTA), and
Probability of threat of amputation (ECCM)
0.11
concluded that MRA and CTA are superior to Doppler ultrasonography with
significantly higher confidence and less additional imaging. Costs were
0.07 0.08 0.09 0.10 0.11 lowest with CTA,
32
but Ouwendijk et al. did not take into account
Probability of threat of amputation (GF)
gadofosveset-enhanced MRA. In our economic modelling, the cost-
effectiveness of gadofosveset-enhanced MRA was investigated compared
with ECCM-enhanced MRA and DSA. We did not take into account the less
Payer perspective, base case I. Details as for Figure 2.
frequently used imaging option CTA as it is not the preferred option in
Intermittent Claudication patients with CLI due to the often heavily calcified peripheral arterial system.
A decision tree was used to model the diagnostic confidence (confident/
Base-case Analysis not confident) with regard to costs for the subsequent management of the
For both the payer and the hospital perspective (except base case II from patient. Data from several sources (e.g. published data and data obtained
the hospital perspective), the management of PAOD initially using from experienced clinicians such as the Delphi panel) were obtained
gadofosveset-enhanced MRA is less costly, while showing equivalent to conduct the analysis. Several randomised clinical studies are ongoing to
utility to ECCM-enhanced MRA or standard DSA. For base case II, observe the diagnostic confidence of the three imaging procedures – DSA
gadofosveset-enhanced MRA and ECCM-enhanced MRA are used more and gadofosveset- and ECCM-enhanced MRA – within the same trial
often if diagnostic confidence is not obtained from the first modality. The setting. As these data are not yet available, data from the Delphi panel were
results of the economic model from both the payer and hospital used for this initial modelling. As soon as these data become available,
perspectives are displayed in Table 3. however, the model should be revised to reflect these results.
Sensitivity Analysis According to the initial cost–utility calculations described in this article,
With regard to sensitivity analyses, the results of the models generally a diagnostic strategy using gadofosveset-enhanced MRA as the initial
stayed robust. However, from a hospital perspective the results for IC diagnostic modality has been shown to be a cost-effective option for the
are more sensitive compared with the results for our other scenarios. work-up of PAOD compared with ECCM-enhanced MRA or with standard
For example, as shown in Figure 4, the advantage of gadofosveset DSA, from both the payer and the hospital perspective, for CLI and IC.
54 EUROPEAN CARDIOLOGY
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