Publications (3)6.77 Total impact
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Article: Developing the clinical components of a complex intervention for a glaucoma screening trial: a mixed methods study.
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ABSTRACT: Glaucoma is a leading cause of avoidable blindness worldwide. Open angle glaucoma is the most common type of glaucoma. No randomised controlled trials have been conducted evaluating the effectiveness of glaucoma screening for reducing sight loss. It is unclear what the most appropriate intervention to be evaluated in any glaucoma screening trial would be. The purpose of this study was to develop the clinical components of an intervention for evaluation in a glaucoma (open angle) screening trial that would be feasible and acceptable in a UK eye-care service. A mixed-methods study, based on the Medical Research Council (MRC) framework for complex interventions, integrating qualitative (semi-structured interviews with 46 UK eye-care providers, policy makers and health service commissioners), and quantitative (economic modelling) methods. Interview data were synthesised and used to revise the screening interventions compared within an existing economic model. The qualitative data indicated broad based support for a glaucoma screening trial to take place in primary care, using ophthalmic trained technical assistants supported by optometry input. The precise location should be tailored to local circumstances. There was variability in opinion around the choice of screening test and target population. Integrating the interview findings with cost-effectiveness criteria reduced 189 potential components to a two test intervention including either optic nerve photography or screening mode perimetry (a measure of visual field sensitivity) with or without tonometry (a measure of intraocular pressure). It would be more cost-effective, and thus acceptable in a policy context, to target screening for open angle glaucoma to those at highest risk but for both practicality and equity arguments the optimal strategy was screening a general population cohort beginning at age forty. Interventions for screening for open angle glaucoma that would be feasible from a service delivery perspective were identified. Integration within an economic modelling framework explicitly highlighted the trade-off between cost-effectiveness, feasibility and equity. This study exemplifies the MRC recommendation to integrate qualitative and quantitative methods in developing complex interventions. The next step in the development pathway should encompass the views of service users.BMC Medical Research Methodology 01/2011; 11:54. · 2.67 Impact Factor -
Article: Screening for open angle glaucoma: systematic review of cost-effectiveness studies.
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ABSTRACT: To systematically review current evidence on the cost-effectiveness of screening strategies for open angle glaucoma (OAG). Studies that reported both costs and outcomes of alternative screening strategies for OAG were identified by a highly sensitive search of electronic databases (eg, MEDLINE, EMBASE, NHS EED, HTA Database), last search December 2005. Data on costs regarding cases and years of visual impairment prevented, cases of blindness prevented, and cases of OAG detected were extracted. Incremental cost-effectiveness ratios were calculated using data provided in the included studies. Four studies met the inclusion criteria. The latest of these was published in 1997. The screening tests and treatments reported in these studies are now not considered to be best practice. Furthermore, data were not reported in sufficient detail to reinterpret the results of the studies in terms of a common outcome measure. Finally, these studies suffered from methodologic weaknesses that further limit their usefulness for decision making. Currently, there is insufficient economic evidence on which to base recommendations regarding screening for OAG. New technologies, potentially suitable as screening devices, and new treatments are available. Further research, both in terms of economic models and conduct of clinical trials with concurrent economic evaluation, may help inform policy makers regarding cost-effectiveness and acceptability of screening for OAG.Journal of Glaucoma 17(3):159-68. · 1.78 Impact Factor -
Article: The value of myocardial perfusion scintigraphy in the diagnosis and management of angina and myocardial infarction: a probabilistic economic analysis.
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ABSTRACT: Coronary heart disease (CHD) is the most common cause of death in the United Kingdom, accounting for more than 120,000 deaths in 2001, among the highest rates in the world. This study reports an economic evaluation of single photon emission computed tomography myocardial perfusion scintigraphy (SPECT) for the diagnosis and management of coronary artery disease (CAD). Strategies involving SPECT with and without stress electrocardiography (ECG) and coronary angiography (CA) were compared to diagnostic strategies not involving SPECT. The diagnosis decision was modeled with a decision tree model and long-term costs and consequences using a Markov model. Data to populate the models were obtained from a series of systematic reviews. Unlike earlier evaluations, a probabilistic analysis was included to assess the statistical imprecision of the results. The results are presented in terms of incremental cost per quality-adjusted life year (QALY). At prevalence levels of CAD of 10.5%, SPECT-based strategies are cost-effective; ECG-CA is highly unlikely to be optimal. At a ceiling ratio of Pound 20,000 per QALY, SPECT-CA has a 90% likelihood of being optimal. Beyond this threshold, this strategy becomes less likely to be cost-effective. At more than Pound 75,000 per QALY, coronary angiography is most likely to be optimal. For higher levels of prevalence (around 50%) and more than a Pound 10,000 per QALY threshold, coronary angiography is the optimal decision. SPECT-based strategies are likely to be cost-effective when risk of CAD is modest (10.5%). Sensitivity analyses show these strategies dominated non-SPECT-based strategies for risk of CAD up to 4%. At higher levels of prevalence, invasive strategies may become worthwhile. Finally, sensitivity analyses show stress echocardiography as a potentially cost-effective option, and further research to assess the relative cost-effectiveness of echocardiography should also be performed.Medical Decision Making 27(6):772-88. · 2.33 Impact Factor
