The potential cost-effectiveness (CE) of adopting innovative procedures within a publically funded healthcare system is a recurring issue.[1] Trans-catheter aortic valve insertion (TAVI) is not currently provided by the devolved National Health Service (NHS) in Scotland, although a single high quality randomised controlled clinical trial (RCT) has demonstrated that TAVI is a clinically effective intervention for reducing the risk of death in older patients with severe aortic stenosis considered unfit for standard surgery.[2] The recently published CE analysis of TAVI reports an incremental CE ratio (ICER) of 16,000 [pounds sterling] per quality adjusted life year (QALY) gained, which falls below the ICER thresholds applied by the National Institute for Health and Clinical Excellence (NICE) in the UK.[1]

The science-consultancy company 'Oxford Outcomes' constructed their CE model based on New York Heart Association (NYHA) category data obtained in the original RCT.[2] This involved adopting a rather convoluted approach of indirectly estimating EQ-5D (EuroQol) values ('utilities') based on data concerning the relationship between NHYA categories and EQ- 5D in patients with heart failure, and on UK population norms that are now almost 20 years old.[1] Given that individual patients in the original RCT had their EQ-5D values measured directly (at baseline, one, six and 12 months) it is not clear why 'Medtronic' (the TAVI-device manufacturer who funded both the original RCT and the CE analysis) did not release the ED- 5D data to 'Oxford Outcomes'. Other important clinical values are derived from a 'literature review' and estimates made by a 'clinical steering group'. Unfortunately making an informed judgement about the validity of these values is difficult as the literature search strategy is not described and membership of the 'steering group' is not reported.

Historically the assessment of CE in the cardiovascular arena has predominantly related to drug therapies, but the approach is now increasingly being applied to cardiovascular devices.[3] Unfortunately CE studies, with their heavy reliance on statistical modelling based on multiple assumptions, have a poor track record of providing unbiased information for healthcare decision making. In a previous systematic review of almost 500 CE studies, industry-sponsored studies were 2-3 times more likely to report favourable results compared to non-industry funded analyses.[4] This may be because the biomedical industry regards the undertaking and reporting of CE analyses as a marketing tool, rather than as an independent scientific endeavour.[3] Consequently clinicians and policy-makers need to be both cautious and critical in assessing this type of study. In our opinion a further replication of these CE findings are required using the EQ-5D data from the original trial.

[1] Watt M, Mealing S, Eaton J, et al. Cost-effectiveness of transcatheter aortic valve replacement in patients ineligible for conventional aortic valve replacement. Heart 2012;98:370-6.

[2] Leon MB, Smith CR, Mack M, et al. PARTNER Trial Investigators. Transcatheter aortic-valve implantation for aortic stenosis in patients who cannot undergo surgery. N Engl J Med 2010;363:1597-607.

[3] Tarricone R, Drummond M. Challenges in the clinical and economic evaluation of medical devices: the case of transcatheter aortic valve implantation. J Med Marketing 2011;11:221-229.

[4] Bell CM, Urbach DR, Ray JG, Bayoumi A, Rosen AB, Greenberg D, Neumann PJ. Bias in published cost effectiveness studies: systematic review. BMJ 2006;332:699-703.

Conflict of Interest:

None declared

Patients eligible for the TAVI intervention are old (>75), face a high mortality risk and generally have multiple comorbidities [1]. Health care consumption of this group of patients can therefore expected to be high [2,3]. As a consequence, life extension in this group would probably result in additional health care consumption in so-called life years gained. Health care consumption in life years gained could be due to treatment of a large variety of diseases related to old age and/or consumption of long-term care due to disabilities.

In the article by Watt et al. [4] only a limited set of cost categories is included, which results in too favourable estimates of the cost effectiveness of TAVI. Current NICE guidelines do not advocate the inclusion of medical costs in life years gained of diseases not directly related to the intervention under study [5]. Ignoring costs that are relevant for the NHS is difficult to defend using scientific arguments [6- 8]. It also results in favoring interventions that primarily increase length of life over interventions that mainly improve quality of life [9]. Broadening the perspective beyond the NHS, as Watts et al. suggest, would probably result in even less favourable cost effectiveness estimates as the target group of TAVI does not participate in the labour market anymore and therefore consumes more than they produce [9]. While there may be uncomfortable implications of including more cost categories that warrant discussion, this can never be a reason to exclude foreseeable costs.

References

1. Leon MB, Smith CR, Mack M, et al. Transcatheter aortic-valve implantation for aortic stenosis in patients who cannot undergo surgery. New Engl J Med 2010; 363: 1597-607

2. Yang Z, Norton EC, Stearns SC.J Gerontol B Psychol Sci Soc Sci. 2003 Jan;58(1):S2-10.Longevity and health care expenditures: the real reasons older people spend more.

3. Basu A, Arondekar BV, Rathouz PJ.Scale of interest versus scale of estimation: comparing alternative estimators for the incremental costs of a comorbidity. Health Econ. 2006 Oct;15(10):1091-107.

4. Watt M, Mealing S, Eaton J, Piazza N, Moat N, Brasseur P, Palmer S, Busca R, Sculpher M.Cost-effectiveness of transcatheter aortic valve replacement in patients ineligible for conventional aortic valve replacement. Heart. 2012 Mar;98(5):370-6. Epub 2011 Nov 10.

5. ISPOR. Pharmacoeconomic Guidelines Around The World. Available at: http://www.ispor.org/PEguidelines/index.asp. Accessed 08/18, 2011.

6. Rappange DR, van Baal PH, van Exel NJ, Feenstra TL, Rutten FF, Brouwer WB. Unrelated medical costs in life-years gained: should they be included in economic evaluations of healthcare interventions? Pharmacoeconomics 2008;26(10):815-830.

7. Meltzer D. Response to "Future costs and the future of cost- effectiveness analysis". J.Health Econ. 2008 Jul;27(4):822-825.

8. Feenstra TL, van Baal PH, Gandjour A, Brouwer WB. Future costs in economic evaluation. A comment on Lee. J.Health Econ. 2008 Dec;27(6):1645- 9; discussion 1650-1.

9. Meltzer D. Accounting for future costs in medical cost- effectiveness analysis. J.Health Econ. 1997 Feb;16(1):33-64.

Conflict of Interest:

None declared