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DOI: 10.1148/radiol.2402050223
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(Radiology 2006;240:401-410.)
© RSNA, 2006

Evidence-Based Practice

Peripheral Arterial Disease: Clinical and Cost Comparisons between Duplex US and Contrast-enhanced MR Angiography—A Multicenter Randomized Trial1

Marianne de Vries, MD, Rody Ouwendijk, MD, Karin Flobbe, PhD, Patricia J. Nelemans, MD, PhD, Alphons G. Kessels, MD, MSc, GeertWillem H. Schurink, MD, PhD, J. Adam van der Vliet, MD, PhD, Frans M. J. Heijstraten, MD, PhD, Philippe W. M. Cuypers, MD, PhD, Lucien E. M. Duijm, MD, PhD, Jos M. A. van Engelshoven, MD, PhD, M. G. Myriam Hunink, MD, PhD and Michiel W. de Haan, MD, PhD

1 From the Departments of Radiology (M.d.V., K.F., J.M.A.v.E., M.W.d.H.), Epidemiology (P.J.N.), Clinical Epidemiology and Medical Technology Assessment (A.G.K.), and Vascular Surgery (G.H.S.) and Cardiovascular Research Institute Maastricht (M.d.V., G.H.S., J.M.A.v.E., M.W.d.H.), Maastricht University MC, P. Debyeplein 25, 6202 AZ Maastricht, the Netherlands; Departments of Radiology (R.O., M.G.M.H.) and Epidemiology and Biostatistics (R.O., M.G.M.H.), Erasmus MC Rotterdam, Rotterdam, the Netherlands; Departments of Vascular Surgery (J.A.v.d.V.) and Radiology (F.M.J.H.), University Medical Ctr, Nijmegen, the Netherlands; and Departments of Vascular Surgery (P.W.M.C.) and Radiology (L.E.M.D.), St Catharina Hospital, Eindhoven, the Netherlands. Received February 9, 2005; revision requested April 8; revision received May 29; accepted June 21; final version accepted October 4. Supported by the Netherlands Organization for Health Research and Development. Address correspondence to M.d.V. (e-mail: mdvr{at}rdia.azm.nl).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Purpose: To prospectively determine the clinical and economic consequences of replacing duplex ultrasonography (US) with contrast material–enhanced magnetic resonance (MR) angiography for the initial imaging work-up of patients with peripheral arterial disease (PAD).

Materials and Methods: This randomized multicenter study was approved by the institutional review board of each hospital, and all patients signed written informed consent prior to randomization. Patients with PAD who needed to undergo imaging work-up and who had an ankle-brachial pressure index (ABPI) of less than 0.90 were recruited by vascular surgeons between January 2002 and September 2003. Patients were randomly assigned to undergo contrast-enhanced MR angiography or duplex US. The primary outcome measure was cost. Secondary outcome measures included therapeutic confidence, changes in disease severity, and changes in quality of life (QOL) assessed during 6 months of follow-up. Indicators for disease severity were based on the Rutherford classification, treadmill walking distance, ABPI at rest, and ABPI after exercise. QOL was assessed with the Rating Scale, Short Form 36, EuroQol-5D, and VascuQol questionnaires. The cost of (additional) imaging procedures, therapeutic interventions, and outpatient visits were calculated from a hospital perspective (ie, all costs incurred inside the hospital were estimated, including physician costs). Data were evaluated by using the Student t test and a multivariable linear regression analysis.

Results: At 6 months, 352 patients (239 [68%] men, 113 [32%] women; mean age, 65 years) were analyzed. The use of contrast-enhanced MR angiography versus duplex US reduced the number of additional vascular imaging procedures by 42%; contrast-enhanced MR angiography was also associated with higher therapeutic confidence. Diagnostic costs for contrast-enhanced MR angiography were {euro}167 ($186) higher than those for duplex US (P < .001). No statistically significant differences were found for total cost, changes in disease severity, or changes in QOL between patients examined with duplex US and those examined with contrast-enhanced MR angiography (P > .05).

Conclusion: Replacing duplex US with contrast-enhanced MR angiography for the initial imaging work-up of patients with PAD reduces the need for additional imaging, although diagnostic costs are higher.

© RSNA, 2006


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
A challenge in the imaging work-up of patients with peripheral arterial disease (PAD) is choosing the best imaging modality that will provide all the information needed and that is cost-effective. PAD of the lower legs is a common and disabling disease (1,2). Revascularization strategies for patients with PAD require assessment by means of imaging work-up. If revascularization is being considered, most centers in the Netherlands use duplex ultrasonography (US) as the initial imaging modality, which is sometimes followed by digital subtraction angiography (DSA) (3,4). Only a few centers use contrast material–enhanced magnetic resonance (MR) angiography as the initial imaging modality for detecting stenoses in patients with PAD.

Duplex US is a well-established noninvasive modality with good sensitivity and specificity (5). The performance of this modality can be further improved by the addition of functional (color flow) imaging (6). Duplex US, however, is operator dependent and does not provide an easy-to-interpret image ("road map") of the vascular system that is useful for treatment planning. Finally, it is often difficult to depict the infrapopliteal vessels with duplex US.

Some researchers prefer contrast-enhanced MR angiography to duplex US for several reasons (7,8). An often-mentioned argument is that contrast-enhanced MR angiography produces a road map of the arteries, thereby making contrast-enhanced MR angiography a more effective tool for treatment planning compared with duplex US. Moreover, some study results have shown that contrast-enhanced MR angiography is more effective for treatment planning than duplex US or even DSA (8–11). In addition, Visser and Hunink (7) performed a meta-analysis that showed contrast-enhanced MR angiography as having better discriminatory power than duplex US. On the other hand, contrast-enhanced MR angiography has disadvantages in that it requires the administration of a contrast agent, and some patients have contraindications to MR imaging.

Despite favorable reports on contrast-enhanced MR angiography, many centers use this technique as an additional examination instead of as an initial examination. It is not currently known whether contrast-enhanced MR angiography or duplex US is more cost-effective for initial imaging in everyday clinical practice.

Thus, the purpose of our study was to prospectively determine the clinical and economic consequences of replacing duplex US with contrast-enhanced MR angiography for the initial imaging work-up of patients with PAD.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Setting, Patients, and Randomization
The present study was a prospective multicenter study in which patients with PAD were randomized between contrast-enhanced MR angiography and duplex US to compare imaging work-up strategies. Two university hospitals and one general hospital (all in the Netherlands) participated in the study. Between January 2002 and September 2003, all patients with PAD who were referred by the vascular surgeons for imaging work-up to evaluate the feasibility and choice of revascularization procedure were eligible for enrollment. The study population consisted of patients with intermittent claudication or critical ischemia and an ankle-brachial pressure index (ABPI) of less than 0.90. Patients were excluded if they needed to undergo imaging work-up within 3 days, had contraindications to MR angiography, or had already undergone previous imaging work-up, indicating that revascularization was needed.

The study was approved by the institutional review board of each hospital, and all patients signed written informed consent prior to randomization. Randomization was performed centrally and took place through the trial coordinating center by telephone. The random allocation scheme used a computer-generated block design, with a block size of eight. The patients, the referring vascular surgeons, and the research assistants were all unaware of the randomization sequence. Given the nature of the procedure, patients and physicians were not blinded to the assigned imaging work-up.

Imaging and Evaluation
Each participating hospital was equipped with state-of-the-art MR imagers (1.5 T) and duplex US equipment. Because of the variety of manufacturers and models of imaging equipment, each hospital was allowed to use the imaging protocols that it considered to be optimal (Table 1). Radiologists (F.M.J.H., L.E.M.D., M.W.d.H.) interpreted images as part of their normal workflow.


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  		Table 1. Protocols for Duplex US and Contrast-enhanced MR Angiography

 
In all three hospitals, duplex US was performed by experienced ultrasonographers (7–15 years of experience). After randomization, the referring vascular surgeon (G.H.S., J.A.v.d.V., or P.W.M.C.) determined the extent of the duplex US examination (imaging of aortoiliac and/or femoropopliteal arteries only or imaging of crural ateries needed) on the basis of patient history and physical examination findings.

Outcome Measures
The outcome measures were therapeutic confidence, changes in disease severity, changes in quality of life (QOL), and costs during 6 months of follow-up.

Provided that no clinically relevant difference in QOL was observed between patients imaged with contrast-enhanced MR angiography and those imaged with duplex US, our primary outcome measures were total cost and total diagnostic cost.

During a weekly vascular conference, therapeutic confidence was assessed with respect to the confidence of the radiologists and vascular surgeons in their ability to make a therapeutic decision on the basis of the results from each imaging modality. Therapeutic confidence was rated on a scale from 0 (no confidence) to 10 (extremely confident). The final therapeutic confidence score was based on a consensus between the radiologist and vascular surgeon. At each participating hospital, three radiologists (F.M.J.H., L.E.M.D., M.W.d.H.) and four vascular surgeons (including G.H.S., J.A.v.d.V., P.W.M.C.) were involved in the therapeutic confidence assessment. Each radiologist and vascular surgeon involved in the study had at least 7 years of experience in either vascular radiology or vascular surgery. Recommended treatment, as well as whether additional vascular imaging was necessary and performed, was also recorded (M.d.V., G.H.S., J.A.v.d.V., P.W.M.C., R.O.).

Indicators for disease severity included the Rutherford classification, treadmill walking distance, ABPI at rest, and ABPI after exercise. All indicators of disease severity were determined at baseline and 6 months after imaging work-up. The measurements were for ABPI and walking distance were performed by technicians. Rutherford classification was assessed by the vascular surgeon (G.H.S., J.A.v.d.V., P.W.M.C.) who treated the patient.

Changes in QOL were assessed by using the Rating Scale questionnaire (12), two generic questionnaires (Short Form 36 [13,14] and Euroqol-5D [15]), and a disease-specific questionnaire (VascuQol [16]); these questionnaires were completed by the patients at baseline and 2 weeks, 3 months, and 6 months after imaging work-up. Patients returned the questionnaires by mail. We selected the four most responsive health dimensions on the Short Form 36 questionnaire for patients with PAD—that is, physical functioning, role physical, bodily pain, and general health (14,16,17).

Costs
Cost calculations were performed from a hospital perspective, which means that all costs incurred inside the hospital were estimated according to the Dutch guidelines for cost calculations in health care (18). To calculate the mean total cost per imaging strategy per patient, we collected all diagnostic costs, outpatient visit costs, physician costs, and therapeutic costs. Costs were collected (M.d.V., R.O., K.F., M.W.d.H., F.M.J.H., L.E.M.D.) at each hospital 6 months after the date of the initial imaging work-up and were reported in euros and U.S. dollars for the year 2002 (the exchange rate was 90 {euro} cents per U.S. dollar in January of 2002).

Diagnostic costs consisted of the costs for initial and additional vascular imaging and were computed by adding the directly assignable and nondirectly assignable costs.

Directly assignable costs included costs for equipment (such as investment), dedicated MR coils, maintenance, room construction, personnel, and materials. The equipment costs were computed by adding the annualized costs of radiologic equipment and the annual costs of equipment maintenance; both costs were divided by the proportion of the total available room time (80% of a 40-hour work week and an annual 3% discount rate) (18–20). Personnel costs were calculated by multiplying the mean wages for each personnel category (including the social security of 37%) by the amount of time spent performing the imaging examination. Material costs were computed by adding the cost of the materials that were used during imaging, such as contrast agents, syringes, and/or interventional catheters.

Nondirectly assignable costs included costs for housing, supporting departments, and overhead. Housing costs for the radiology rooms were based on the housing costs per square meter per year multiplied by the room surface. Costs for the supporting departments were based on the records of the Financial and Economics Department of each hospital. The overhead costs were estimated to be 15% of the directly assignable costs (18). Therapeutic costs included costs for percutaneous vascular interventions (ie, percutaneous angioplasty, stent placement, and thrombolysis), vascular surgery (ie, bypass surgery, endarteriectomy, and amputation), and associated hospital admissions or complications. Costs of vascular surgery and diagnostic procedures were measured and calculated in a similar fashion by using data from another comparable study (21). Costs for the number of outpatient visits, the number of days in the hospital, and/or intensive care admissions were based on national estimates in the Netherlands (18).

Statistical Analysis
The results were analyzed in consensus (M.d.V., R.O., A.G.K., K.F., P.J.N., M.W.d.H., J.M.A.v.E., M.G.M.H.) and according to the intention-to-diagnose-and-treat principle and the Consolidated Standards for Reporting of Trials guidelines (22,23). As a result, patients who died during follow-up were not excluded from cost analysis, and the worst possible scores were used to represent QOL at 6-month follow-up. For all other patients, data that were missing because questionnaires had not been returned were excluded from the analysis for changes in QOL. Missing items on returned questionnaires were imputed by using the mean value of that variable.

The intent of the study was to test for a difference between diagnostic work-up costs and total costs while QOL and other patient outcomes were not detrimentally affected. The sample size calculation (M.G.M.H.) was therefore based on QOL outcomes because we believe that it would be essential not to miss a clinically relevant difference in this outcome measure. At the same time, we ensured that the sample size would be adequate to demonstrate a difference between total diagnostic cost and total cost per patient. It was expected that 40%–50% of the patients would have considerable improvement in their symptoms after treatment, as demonstrated by the bodily pain and physical functioning categories on the Short Form 36 questionnaire (14). To detect a clinically important difference of more than 15% with a power of 80% and a two-tailed {alpha} level of .05, we calculated a final target sample of 340 patients. Anticipating a 5% dropout rate, we set our recruitment goal at 357 patients.

Differences in costs between duplex US and contrast-enhanced MR angiography were adjusted for baseline characteristics that could potentially influence the outcomes. Therefore, according to the TransAtlantic Inter-Society Consensus (24), the following determinants at baseline were considered to potentially influence outcomes: the presence of renal diseases (ie, renal transplantation or renal insufficiency), cardiac diseases, cerebrovascular diseases, or diabetes mellitus; disease severity (critical ischemia vs claudication); hospital setting; and study group. These determinants were entered (at once) in a multivariable linear regression analysis. The ß coefficient of the study group reflected the adjusted difference in cost between contrast-enhanced MR angiography and duplex US.

A Student t test was used to test for differences between the other outcome measures for both imaging work-up strategies. Because multiple statistical tests were performed, a P value of .01 or less was considered to indicate a statistically significant difference. All analyses were performed by two authors (M.d.V., R.O.) who used a commercially available statistical software program (SPSS, version 11.0; SPSS, Chicago, Ill).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
A total of 720 patients were evaluated for trial eligibility, and 363 patients were excluded for various reasons. The Figure shows more details on the flow of patients through the trial. After randomization, 180 patients were allocated to undergo contrast-enhanced MR angiography, and 177 patients were allocated to undergo duplex US. Two patients in the contrast-enhanced MR angiography group and three patients in the duplex US group either died or withdrew from the study prior to imaging; these patients were therefore excluded from analysis. Consequently, the cost analysis was performed in 178 patients in the contrast-enhanced MR angiography group and in 174 patients in the duplex US group. During follow-up, four patients died in the contrast-enhanced MR angiography group, and five patients died in the duplex US group.


Figure 1
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  		Flow chart demonstrates the number of interventional procedures (*) that were performed, with some patients undergoing several procedures. Patients who were lost to follow-up ({dagger}) were those who did not undergo imaging.

 
The distribution of baseline characteristics was similar in the contrast-enhanced MR angiography and duplex US groups (Table 2). Comorbidity, however, occurred slightly more often in the contrast-enhanced MR angiography group. The distribution of the severity of PAD, expressed according to the Rutherford classification, was equal for both groups. In the contrast-enhanced MR angiography group, 19 (11%) of 178 patients had critical ischemia; in the duplex US group, 20 (11%) of 174 patients had critical ischemia.


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  		Table 2. Baseline Characteristics

 
Outcome Measures
Contrast-enhanced MR angiography and duplex US were associated with high therapeutic confidence scores for making a treatment decision after imaging work-up. The mean therapeutic confidence score was significantly higher for the contrast-enhanced MR angiography group than for the duplex US group (8.2 vs 7.5, respectively; P < .001).

With respect to changes in Rutherford classification, maximum treadmill walking distance, ABPI at rest, and ABPI after exercise, there was no statistically significant difference between groups with respect to improvement of disease severity (Table 3).


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  		Table 3. Change in Outcome Measurements after Follow-up

 
The return rates for the QOL questionnaires were 98% (346 of 352 questionnaires) at baseline, 95% (335 of 352 questionnaires) at 2 weeks, 91% (322 of 352 questionnaires) at 3 months, and 88% (309 of 352 questionnaires) at 6 months. Moreover, all of the returned questionnaires had high completion rates that varied from 97.2% to 99.7% for the individual dimensions. There were no statistically significant differences in improvement of QOL at 2 weeks, 3 months, and 6 months for the contrast-enhanced MR angiography group compared with the duplex US group (Table 3).

Before therapy, 19 additional vascular imaging examinations were performed in the contrast-enhanced MR angiography group, whereas 47 additional vascular imaging examinations were performed in the duplex US group (Table 4). During the 6 months of follow-up, a total of 40 additional vascular imaging examinations were performed in the contrast-enhanced MR angiography group compared with 69 additional vascular imaging examinations in the duplex US group. Thus, the total number of additional vascular imaging examinations was reduced by 42% in the contrast-enhanced MR angiography group (P < .001). For the duplex US group, these additional examinations mainly consisted of DSA and contrast-enhanced MR angiography. The total number of additional diagnostic DSA examinations was reduced by 63% in the contrast-enhanced MR angiography group compared with the duplex US group (11 vs 30 DSA examinations, respectively; P = .001). Twenty additional contrast-enhanced MR angiography examinations were performed in the duplex US group compared with one additional contrast-enhanced MR angiography examination performed in the contrast-enhanced MR angiography group.


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  		Table 4. Number of Imaging Examinations and Interventions, with Distribution of Costs

 
Costs
Overall, the mean total cost per patient, which consisted of all diagnostic, therapeutic, and outpatient visit costs, was {euro}272 ($302) higher in the contrast-enhanced MR angiography group than in the duplex US group (Table 4). This difference was not significant (95% confidence interval: –{euro}377, {euro}921 [–$419, $1023]; P = .41).

The mean unit cost for the initial examination per patient was {euro}105 ($117) for duplex US and {euro}473 ($526) for contrast-enhanced MR angiography. The mean cost for total additional imaging per patient during the 6 months of follow-up was {euro}118 ($131) in the contrast-enhanced MR angiography group and {euro}323 ($359) in the duplex US group (Table 4). The total additional imaging costs were significantly lower in the contrast-enhanced MR angiography group than in the duplex US group (mean difference, {euro}202 [$224] per patient; P < .001). Although contrast-enhanced MR angiography was associated with lower total additional imaging costs, the total diagnostic cost of contrast-enhanced MR angiography was {euro}167 ($186) higher than that of duplex US (P < .001). One-way sensitivity analysis showed that the higher total diagnostic cost for contrast-enhanced MR angiography was explained by the higher cost of the initial imaging test, which was the result of the high investment cost for the MR imaging unit. In the one-way sensitivity analysis, the investment costs for the MR imager were reduced by 50%, which resulted in a nonstatistically significant difference in the total diagnostic cost between contrast-enhanced MR angiography and duplex US (adjusted difference, {euro}52 [$58]; 95% confidence interval: –{euro}33, {euro}138 [–$37, $153]; P = .23).

Furthermore, the costs for outpatient visits (Table 4) were not significantly different between the contrast-enhanced MR angiography group and the duplex US group (P = .30). The number and cost of revascularization procedures performed by using percutaneous transluminal angioplasty and surgical procedures were not significantly different between groups (P > .05).

A subgroup analysis showed no statistically significant difference in total additional imaging cost, total diagnostic cost, and total cost for duplex US and contrast-enhanced MR angiography between the three hospitals.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
ADVANCES IN KNOWLEDGE
 References
 
Contrast-enhanced MR angiography and duplex US performed equally well for initial imaging work-up in patients with PAD, although the two imaging modalities had different qualities that counted in their favor. Contrast-enhanced MR angiography reduced the number of additional vascular imaging examinations and improved the therapeutic confidence score. On the other hand, duplex US was associated with a significantly lower total diagnostic cost compared with contrast-enhanced MR angiography because of the high investment cost of the MR imager. The total cost (ie, all diagnostic costs, therapeutic costs, and outpatient visit costs), as well as improvement in QOL and disease severity after 6 months, was comparable for both groups.

Ultimately, the choice between duplex US and contrast-enhanced MR angiography for initial imaging work-up in patients with PAD will depend on the local expertise of those who perform the technique and the cost considerations that are relevant to the particular setting. Provided that the ultrasonographers who are performing the examination are highly experienced, duplex US has very good results for sensitivity and specificity, even with regard to the depiction of the lower legs (25–27). Similarly, the image quality of MR angiography depends on the quality of the equipment and the experience of the MR technologists. For example, high spatial resolution is a prerequisite for optimal depiction of the vascular tree, and high temporal resolution is important to avoid projection of disturbing veins over the arteries. As a result, dedicated MR receiver coils, up-to-date imaging protocols, and the use of contrast agents are necessary to obtain optimal image quality. Study results have shown that MR angiography performed without the use of contrast agents (eg, by using time-of-flight sequences) has reduced diagnostic accuracy compared with MR angiography performed with the use of contrast agents (28,29).

A major advantage of duplex US is that the total diagnostic costs are lower compared with those of contrast-enhanced MR angiography. The higher total diagnostic cost of contrast-enhanced MR angiography is explained by the higher cost of the initial contrast-enhanced MR angiography examination, particularly because of the high investment cost of the MR imager. It should be noted, however, that MR angiography is a relatively new imaging technique, and this newness may, in part, explain the high investment costs. One may expect that, in the future, these costs will decrease as MR imagers become more widely available. As was shown in our study, with a 50% reduction in the investment costs of the MR imager, the total diagnostic costs were almost equal between contrast-enhanced MR angiography and duplex US. Furthermore, although the difference in diagnostic costs was statistically significant, the magnitude of the difference was not very large, and a department may consider the additional expense to be justified.

The use of contrast-enhanced MR angiography resulted in a lower need for additional vascular imaging, particularly for diagnostic DSA examinations, compared with duplex US. This finding was in accordance with the findings of Leiner et al (8) who showed that surgeons who had to define treatment plans were less likely to request diagnostic DSA after contrast-enhanced MR angiography than after duplex US.

In our study, the reduction in additional vascular imaging examinations is consistent with the significantly higher therapeutic confidence score after contrast-enhanced MR angiography compared with duplex US. The higher therapeutic confidence of the surgeons after contrast-enhanced MR angiography indicates that treatment planning was more efficient with contrast-enhanced MR angiography than with duplex US. An explanation is that contrast-enhanced MR angiography presents the arteries as a road map, which allows better visualization of the location, severity, and extent of stenosis and better quality of the outflow arteries.

Although treatment planning was more efficient after contrast-enhanced MR angiography, neither contrast-enhanced MR angiography nor duplex US seemed to influence the therapeutic decision, as is suggested by the fact that the number and nature of the interventional procedures, as well as the therapeutic costs, were similar for both groups. The foremost contributors of the total cost were the costs of therapy and possible complications after therapy (30). Our study also showed that, despite the higher total diagnostic cost for the contrast-enhanced MR angiography group, similar therapeutic costs resulted in a similar total cost for duplex US and contrast-enhanced MR angiography groups.

Our study had several limitations. It is expected that the contrast-enhanced MR angiography strategy might be more cost-effective in patients with critical ischemia. These patients often undergo distal bypass surgery and require more adequate depiction of the lower leg arteries, which may be better seen with contrast-enhanced MR angiography. In our study, however, only 39 (11%) of 352 patients had critical ischemia; consequently, this group was too small to allow a separate subgroup analysis.

Another study limitation was that the computation of costs was performed from a hospital perspective instead of from a societal perspective, as is frequently recommended (22,23). Calculating costs according to the societal perspective requires adding all costs inside and outside the health care sector, such as direct costs (patient costs) and indirect costs (costs due to production losses). We chose a hospital perspective because previous cost analyses concerning the care of patients with PAD showed that patient costs were relatively low for settings in both the Netherlands and the United States (31,32). Furthermore, the majority of the patients with PAD were retired from the workforce; therefore, costs for production losses would have been negligible (33).

Several small imbalances in the distribution of baseline characteristics between the contrast-enhanced MR angiography and duplex US groups were observed despite randomization. For example, comorbidity occurred somewhat more frequently in the contrast-enhanced MR angiography group than in the duplex US group. Although the differences were small, we adjusted for relevant baseline characteristics in a multivariable linear regression analysis. In addition, we adjusted for hospital setting.

In conclusion, we believe that the choice between duplex US and contrast-enhanced MR angiography for initial imaging work-up in patients with PAD may very well depend on the local expertise of those who perform these techniques and the cost considerations that are relevant to the local setting. Replacing duplex US with contrast-enhanced MR angiography for initial imaging work-up in patients with PAD reduces the need for additional imaging, although the diagnostic costs are higher.


   ADVANCES IN KNOWLEDGE
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
References
 


   FOOTNOTES
 

Abbreviations: ABPI = ankle-brachial pressure index • DSA = digital subtraction angiography • PAD = peripheral arterial disease • QOL = quality of life

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, M.d.V., R.O., K.F., P.J.N., J.M.A.v.E., M.G.M.H., M.W.d.H.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, M.d.V., R.O., J.M.A.v.E., M.G.M.H.; clinical studies, all authors; statistical analysis, M.d.V., R.O., K.F., P.J.N., A.G.K., M.G.M.H.; and manuscript editing, all authors


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 

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R. Ouwendijk, M. de Vries, T. Stijnen, P. M. T. Pattynama, M. R. H. M. van Sambeek, J. Buth, A. V. Tielbeek, D. A. van der Vliet, L. J. SchutzeKool, P. J. E. H. M. Kitslaar, et al.
Multicenter Randomized Controlled Trial of the Costs and Effects of Noninvasive Diagnostic Imaging in Patients with Peripheral Arterial Disease: The DIPAD Trial
Am. J. Roentgenol., May 1, 2008; 190(5): 1349 - 1357.
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