Systematic Review of Utilities in Abdominal Aortic Aneurysm

Article Outline

• Abstract
• Introduction
• Materials and Methods
  • Utility measurement
• Results
  • General findings
  • Utility results in EVAR versus open repair
  • Utility results in screening and rupture
  • Utility results with visual analogue scale (VAS)
• Discussion
• Conclusion
• Acknowledgements
• Appendix
  • The EQ-5D
• Conflict of Interest
• References
• Copyright

Abstract 

Introduction

Two main treatments exist for the repair of abdominal aortic aneurysm (AAA). Open surgical repair has been the standard treatment, but more recently endovascular aneurysm repair (EVAR) has been introduced as a less invasive technique. To compare the long-term outcomes of these, utility outcomes have been suggested to be relevant.

Objective

to review studies comparing the utility outcomes of open repair and EVAR treatment for AAA.

Design

database search with strict inclusion and exclusion criteria.

Materials and Methods

The search was performed in PubMed and EMBASE covering terms relating to AAA and utility. Studies were analysed qualitatively.

Results

10 studies of AAA met the review criteria. The comparative utility scores for the different treatments varied considerably between studies. A Canadian cohort study estimated EVAR as more favorable than open repair, while randomised controlled trials reported lower utilities with EVAR, except for one month post–surgery in the EVAR 1 trial. Furthermore, after screening for AAA, patients testing positive gave similar QoL-5D scores, but worse visual analogue scores than those testing negative.

Conclusion

There were few studies calculating utilities in AAA, with inconsistent findings. The limited reporting of data prevents in-depth analysis to explain the differences.

Keywords: Abdominal aortic aneurysm (AAA), Open repair, Endovascular aneurysm repair (EVAR), Quality of life (QoL), Utility, Health technology appraisal

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Introduction 

The primary goal of surgical treatment of abdominal aortic aneurysms (AAA) is the prevention of death from rupture. Open surgical repair (OR) of AAA is considered to be the established treatment, but in recent years has been compared with endovascular aneurysm repair (EVAR).¹, ², ³ Data from the randomised controlled trials demonstrated that EVAR had a lower immediate mortality than open surgery and conferred an advantage in aneurysm related mortality up to 4 years follow-up. The trials also demonstrated that the endovascular technique was more expensive and had a significant number of complications in the post-operative period.

The EVAR and Dutch Randomised Endovascular Aneurysm Management (DREAM) trials included patient utility assessments. Utilities for a given health state represent the preference that individuals have for this health state.⁴ Utilities can be conceptualized as a single summary measure of health-related quality of life (HRQL) with the anchors of one corresponding to perfect health and zero corresponding to death.⁵, ⁶ Utilities are usually used to estimate quality-adjusted life years (QALYs), providing a generic health-related outcome measure for comparison of different treatments for different patient groups. QALYs, by using the utility data, take into account not only the mortality, but also the quality of life of patients. In chronic disease states, where the quality of life of the patient is impaired for a prolonged period of time, incorporating utilities into the economic evaluation can significantly influence the cost-effectiveness of the intervention. The value of utility assessments in asymptomatic diseases is less well recognized. However, the recognition of the importance of quality of life, led to utility data being essential for economic submissions to reimbursement authorities in many countries. It is therefore important that any cost-effectiveness analysis of EVAR includes utility data, as these data are likely to play a role in any nationally sponsored health technology assessment.

However utility results from randomised controlled trials (RCTs) are not reported consistently and appear to lead to different conclusions. To attempt to understand the differences and to locate any alternative source of utilities for the different procedures and all possible health states in AAA, the available literature on AAA was reviewed.

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Materials and Methods 

An extensive search was performed in MEDLINE and EMBASE, to capture all published studies incorporating utility and general quality-of-life measures for abdominal aortic aneurysm. The same search strategy was utilised for all databases. Search terms covered the therapeutic area (AAA) and quality-of-life/utility terms (quality-of-life, utility, patient reported outcomes, quality adjusted life-years, QALY*, Euroqol, EQ-5D). The limits were human studies and publication from 1995 onwards, with abstract. The term ‘aneurysm’ had to be found in either the title or the abstract. Available technology appraisals were also searched. Studies had to meet all the following inclusion criteria, agreed by reviewers N.M and J.H, to be included in the review:

The exclusion criteria were the following:

No exclusion criteria were set regarding the length of follow-up. The most common cause for exclusion was the study being a review article or the use of disease specific quality-of-life measures only.

The studies were analysed according to study design, patient population, comparators, time horizon, outcomes measures used, the source of utilities and utility and general quality-of-life results. In addition the limitations of the studies were explored.

Utility measurement 

Utility measures can be obtained from clinical studies indirectly using instruments, such as EQ-5D or the Rosser Index, the results of which can be transformed into index utility scores, or directly with the help of methods, such as the visual analogue scale (VAS). The usual scale for utilities has 0.0 for death and 1.0 for perfect health.⁷

The most commonly used utility measure, also used by the 3 RCTs is the EQ-5D supplemented by VAS.

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Results 

General findings 

Using the above search strategy 242 articles were identified. After reviewing the abstracts to apply the inclusion and exclusion criteria, the number of studies was reduced to 38 articles on aneurysm and one technology appraisal prepared for the Ontario Ministry of Health & Long-term Care, for which both the interim⁸ and the final report were available,⁹ as it included an original study of utilities (from this point referred to as the Ontario study).

There was a wide variety of aneurysms assessed; including cerebral and thoracic aneurysms. However, the studies focusing on AAA (25 studies in total¹, ², ³, ⁸, ⁹, ¹⁰, ¹¹, ¹², ¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁷, ¹⁸, ¹⁹, ²⁰, ²¹, ²², ²³, ²⁴, ²⁵, ²⁶, ²⁷, ²⁸, ²⁹) were only of interest in this review. The majority of studies were conducted in the US and Europe.

Only nine of the articles reported utility estimates.¹, ², ³, ⁸, ⁹, ¹¹, ¹², ¹³, ¹⁴, ¹⁵ All of the published studies were found in clinical journals.

Utilities were calculated with the help of EQ-5D in most cases.¹, ², ³, ⁸, ⁹, ¹¹, ¹², ¹³, ¹⁵ Of the studies reporting EQ-5D estimates, four were RCTs comparing EVAR and OR,¹, ², ³ or screening with no screening¹¹; two were prospective cohort studies assessing OR alone or compared with EVAR⁸, ⁹, ¹⁴; one was a case-control study in screening,¹⁵ and one a cross-sectional study after surgery¹² (Table 1).

Table 1. Utility studies in AAA

Reference, Country	Type of data collection	Patient population	Patient number	Health technology used	Follow-up (months)
MASS,11 UK	Prospective RCT	men aged 65–74	no data	screening (after surgery or surveillance)	12
Ontario study,8, 9 Canada	Prospective Cohort	patients with AAA>5.5cm, age 57–93, male 78–83%	314	OR or EVAR	12
EVAR trial 2.1 UK	Prospective RCT	unfit for OR, aged≥60 years, AAA≥5.5cm	338	EVAR or no intervention	12–24
EVAR trial 1.2 UK	Prospective RCT	aged≥60 years, AAA≥5.5cm	1082	OR or EVAR	12–24
Laukontaus et al.12, Finland	Cross sectional	patient underwent surgery for ruptured AAA, mean age 72, male 92%	94	surgery	n.a.
Lottman et al.13, Netherlands	Prospective RCT	eligible for both OR and EVAR, mean age 69, male 72%, mean aneurysm 52 and 56mm	57	OR or EVAR	3
Perkins et al.14, UK	Prospective Cohort	patients after OR, median age 74, male 85%	59	OR	6
DREAM trial,3 Netherlands	Prospective RCT	eligible for both OR and EVAR, mean age 70, male 92% with aneurysms ≥5.0cm	153	OR or EVAR	12
Spencer et al.15, Australia	Prospective Case-control	men aged 65–83, with small AAA (30–49mm)	498	screening	n.a.

Apart from the different aims of the studies, and thus the different comparators, a number of factors prevent comparison across the studies:

Most of the 10 studies assessing utility, also explored quality of life with other instruments. However these instruments, such as the most common general quality of life instrument, SF-36, employed in seven studies,¹, ², ³, ⁸, ⁹, ¹³, ¹⁴, ¹⁵ do not provide utility values.

Thus, although utility data were available for the first 12 months after surgery or screening, usually in 3 to 6 monthly intervals (Table 2), the quantitative synthesis of the results is not possible due to the variation in patient population, comparators, type of utility measurements and reporting.

Table 2. Availability of utility data at different time points

Utility results in EVAR versus open repair 

From the 10 studies, only four reported EQ-5D values for EVAR (Table 3). Comparative utility data were given for patients eligible for both OR and EVAR, with aneurysms at least 5.0–5.5cm in diameter,¹, ², ³, ⁸, ⁹ and for patients unfit for OR¹ at preoperative stage, and at 3 weeks, 6 weeks, 1, 3, 6, 9 and 12 months after the surgery. These studies were difficult to compare due to different reporting formats (effect sizes³ and adjusted values⁸), and different patient populations (patients unfit for OR in EVAR 2 resulting in lower values).

Table 3. Utility results for EVAR

In the Ontario study,⁸, ⁹ although the scores were similar to the EVAR 1 trial results² at one month after the surgery, they were significantly higher from 3 months onwards. However, the area under the curve estimation of the utility for the full 12 months adjusted to baseline differences produces the value (0.843) which was closer to the 12 month result of the EVAR 1 trial.², ⁸ The results from the DREAM trial³ were not comparable as only the changes in scores are given, and the baseline was not reported. Similarly to EVAR, OR data was available from four studies but they were not comparable due to different methodology,¹⁴ and different reporting formats.³, ⁸, ⁹

With the exception of the study by Perkins et al.,¹⁴ all studies demonstrated an initial dip in utilities due to the invasive nature of the intervention, but with different levels of improvement after that.

In the Ontario⁸, ⁹ and EVAR 1 study,² although the results were similar at one year post surgery, the Ontario model used lower estimates for 1 and 3 months, and higher estimates after that, i.e. in the Ontario study patients had worse quality of life immediately after the surgery, but after one year it was better than before surgery. In the case of OR, the area under the curve estimation of the utility for the full 12 months, adjusted to baseline differences (0.777), was even closer to the 12 months result of the EVAR 1 trial,² than in the case of EVAR. The values calculated by Perkins et al.¹⁴ were higher throughout the study period, however instead of EQ-5D, the Rosser index was employed to estimate the utilities. (Table 3)

The relationship between utilities of EVAR and OR varied from study to study. Whilst the DREAM study³ found a trend of lower quality of life with EVAR, which was significant at 6 and 12 months, in EVAR 1² open repair had a significantly lower utility only one month post–surgery. This latter difference cancelled out, and at the end of one year there was no difference between the two procedures. At the same time the Ontario study showed higher estimates for EVAR throughout the whole year after surgery.⁹ This might be due to the Ontario study accounting for major non-EVAR related complications, such as stroke, congestive heart failure (CHF), myocardial infarction (MI) and renal failure, separately.

Although there were studies available comparing the utilities with OR and EVAR, they came to different conclusions regarding the relative efficacy of EVAR. In depth research into the cause of these differences was prevented by the aforementioned incomparability of the studies.

Utility results in screening and rupture 

Utilities for open surgery, of bigger or rapidly expanding aneurysms and surveillance for smaller aneurysms, were calculated in the MASS study.¹¹ Utility scores were similar for both groups preoperatively (0.81), but by 3 and 12 months quality of life was marginally higher with surgery. Spencer et al.¹⁵ assessed patients with and without AAA after screening; however they found no significant difference in utility scores. The utility value for patients undergoing surgery for ruptured aneurysm was calculated by Laukontaus et al.¹² however due to the acute nature of this life threatening condition there was no pre-operative evaluation done. (Table 4)

Table 4. Additional utilities relating to AAA

Utility results with visual analogue scale (VAS) 

Utilities plus VAS scores were assessed in 6 studies¹, ², ¹¹, ¹², ¹³, ¹⁵ However the 2 EVAR trials did not report the VAS findings.¹, ²

Lottman et al.¹³ estimated VAS for EVAR and OR pre-operatively, and 1 and 3 months post-operatively in a small (n=76) patient population. The baseline scores were different for EVAR and OR (67±18 and 61±17 respectively), and they changed only marginally during the study (68±14 and 61±16 at 1 months, 67±18 and 61±17 at 3 months respectively).

In the MASS trial,¹¹ after screening for AAA, patients' quality-of-life score was worse with VAS compared with EQ-5D (76 versus 80). This VAS score improved only in the case of surgery 3 months post operation (90 for surgery, 77 for surveillance), and decreased by the end of one year, although this was still not as low as for surveillance (81 for surgery, 76 for surveillance).¹¹ In another screening program,¹⁵ although there were no significant differences between men before and after screening, either with normal abdominal aorta or with AAA, significantly less men with AAA were likely to have scores ≥80 than without AAA (OR: 0.5, 95% CI: 0.3–0.9). The VAS for patients undergoing surgery for ruptured aneurysm was 61.¹²

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Discussion 

In the field of AAA treatment few studies were found which reported utility estimates, with most using the EQ-5D index score. The main studies were three randomized trials (EVAR 1 and 2,¹, ² DREAM³) and the Ontario cohort study.⁸, ⁹ The scores were usually given at more frequent intervals until approximately 3 months after surgery or screening, and then less frequently for up to one year. The scores for EVAR and OR incorporate complications, with the exception of the Ontario study. In the Ontario study, the utility decrement due to major complications, such as stroke, myocardial infarction, congestive heart and renal failure was accounted for separately, while other complications such as endoleaks were included in the estimates. None of the studies reported separate figures for complications, although the utility for ruptured AAA after surgery was available.

The comparative utility of OR and EVAR varied considerably between the Ontario, the DREAM and the EVAR1 studies, with the Ontario study being the most favorable for EVAR. However the RCT-based evidence from the EVAR and the DREAM trials might be regarded as a higher level than that of the cohort study in the Ontario assessment report.

There is not a good explanation why there is such a difference in the comparative utility results for EVAR and OR between the 3 randomised trials as far as they are comparable. Nevertheless, as utility results have a significant influence on the cost-effectiveness assessment and therefore on economic submissions to reimbursement authorities, some issues should be taken into consideration. The value of utility assessments in asymptomatic diseases is less well recognized. In general a patient with an AAA is asymptomatic and due to the nature of the intervention the patient is expected to return to the pre-operative mental and physical state in time. Complications will have an effect on utility results.

Recent reports from patient registries suggest the possibility of lower complication rates with endovascular repair compared to the ones found by the EVAR and the DREAM trials.³⁰, ³¹, ³² This might be due to more experience with the procedure, as recruitment for the EVAR trials started in 1999, and for the DREAM trial in 2000. A different attitude towards the frequent occurring Type II endoleaks might lead to fewer re-interventions. Lower complication and re-intervention rates would result in higher utilities.

Utility data in most cases are used in cost-utility models calculating the incremental cost per quality-adjusted life-year gained. These trials assist this task by providing data reflecting the surgical experience and complication rates at the time they were undertaken. The assumption that complication rates remain the same, even if more experience is gained with EVAR, seems to be challenged by the recent registry results. The implications of this could have been tested if the utilities in the trials had been reported by different outcomes, such as successful repair, conversion or the various types of complications. However this was outside the scope of both the EVAR and the DREAM trials.

One of the limitations of the study was that it could not take into account the differences in treatment patterns between countries and in time regarding evaluation of the fitness of patients, and the subsequent decision for eligibility for EVAR. Similarly, the effect of varying the complications rates could not be estimated. This would require a re-analysis of the utility data from the randomized trials according the different clinical outcomes, to allow the recalculation of utility results with different complication and conversion rates.

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Conclusion 

There are very few studies calculating utilities in AAA. All published studies were reported in clinical journals with the main purpose of evaluating efficacy and safety, and not to perform an economic analysis. Furthermore, the findings of these studies are not consistent, and the limited and varied reporting of these data prevents further analysis to explain the differences.

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Acknowledgements 

Research was supported by an unrestricted grant from Medtronic International SA.

The Aneurysm Health Economics Advisory Board has assisted in drawing up the methods and in the interpretation of the results. Beside MM Thompson, CV Soong, MRHM van Sambeek and J Hutton, the members of the Aneurysm Health Economics Advisory Board included M Cairols (Bellvitge University Hospital, Barcelona, Spain), F Moll (UMC Utrecht, Utrecht, The Netherlands), E Piccinini (Ospedale Santa Maria delle Croci, Ravenna, Italy), M Puttini (Niguarda, Milan, Italy), M Richer de Forges (Clinique du Pré, Le Mans, France), T Umscheid (Städtische Kliniken Frankfurt-Höchst, Frankfurt, Germany), F Verzini (Azienda Ospedaliera di Perugia, Perugia, Italy).

In the writing of the manuscript we would like to acknowledge the help of Sarah Hearn, United BioSource Corporation, London, UK.

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Appendix 

The EQ-5D 

The EQ-5D is a standardised utility instrument used to measure health outcomes. It is applicable to a wide range of health conditions and treatments, providing a simple descriptive profile and a single index value for health status, and is designed for self-completion by respondents in the form of a straightforward questionnaire.

As part of the descriptive system, the EQ-5D contains five health-related quality of life dimensions: 1) mobility, 2) self-care, 3) usual activity, 4) pain/discomfort, and 5) anxiety/depression. Each dimension is designated three levels defining severity: a) “no problem”, b) “some problem”, and c) “extreme problem”. Subjects are asked to select the category most descriptive of their current level of function or experience for each dimension. Each category response for the dimensions has a different level of negative weighted score attached. The scores vary from dimension to dimension and the sum of these scores represents the final utility score. Perfect health is represented by 1, and 0 represents death.

The classification system has been assigned several different standardised scores derived through population-based samples of respondents asked to assign values to subsets of the 243 states. The most commonly used scoring system is a “tariff” system of weights applied to the dimension levels (and an adjustment for interaction) derived in the United Kingdom from a community sample of persons.³³ A set of valuation weights has been derived from a U.S. sample more recently.³⁴

The visual analogue scale (VAS) is often employed to supplement the EQ-5D index. It measures the quality of life with the help of a thermometer scale, where the current health has to be placed between the two endpoints best possible health and worst possible health. The VAS scores are calculated using perfect health represented by 100, and death represented by 0.

The Rosser Index. The Rosser Index classifies health states along two dimensions. The eight levels of disability and the four levels of distress allows for 32 different health states. Thus it is less sensitive than the EQ-5D and the values for each health state are derived from a small sample.³⁵

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Conflict of Interest 

Noemi Muszbek is an employee of United BioSource Corporation. As a research organisation, United BioSource Corporation conducted the original literature review upon which this article is based with the help of the advisory board. United BioSource has undertaken similar projects for other companies. John Hutton at the time of writing was also an employee of United BioSource Corporation.

Pascale Brasseur is directly employed by Medtronic International SA.

M Thompson, M Cairols, F Moll, E Piccinini, M Puttini, M Richer de Forges, CV Soong, T Umscheid, F Verzini, MRHM van Sambeek have received unrestricted research grants from Medtronic International SA. However, they have not received an honorarium to author this manuscript.

No writing agency has provided editorial support.

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