Is it worthwhile to conduct a randomized controlled trial of glaucoma screening in the United Kingdom?

Abstract

Objectives: To assess the value of conducting a glaucoma screening randomized controlled trial in the UK.

Methods: Decision model based economic evaluation and value of information analysis. Model derived from a previous health technology assessment. Model updated in terms of structure and parameter estimates with data from surveys, interviews with members of the public and health care providers and routine sources.

Results: On average, across a range of ages of initiating screening (40-60 years), glaucoma prevalence (1-5%), screening uptake (30-100%), and the performance of current case finding, screening was not cost-effective at a £30,000 threshold per quality adjusted life year (QALY) from the perspective of the National Health Service (NHS). The societal value of removing all uncertainty around glaucoma screening is £107 million at a threshold of £20,000 per QALY. For informing policy decisions on glaucoma screening, reducing uncertainty surrounding the NHS and personal social care cost of sight impairment (£74 million) was of most value, followed by reducing uncertainty in test performance (£14 million) and uptake of either screening or current eye care (£8 million each).

Conclusions: A glaucoma screening trial in the UK is unlikely to be the best use of research resources. Further research to quantify the costs of sight impairment falling on the NHS and personal social services is a priority. Further development of glaucoma tests and research into strategies to promote the uptake of screening or current eye care such as through the use of a behavioural intervention would be worthwhile.

Keywords: decision analysis; health policy; ophthalmology; public health.

Figure 1.

Strategies with the highest net-benefit (defined as £30,000 × mean QALYs minus mean costs) for alternative values of annual cost of sight impairment and percentage of screening uptake for a 50-year-old cohort. Willingness to pay is £30,000. (a) 1% glaucoma prevalence and 17% uptake current eye care practice. For the range of values selected for the annual cost of sight impairment and uptake rate, only ‘current practice’, ‘GPS11d (IOP + VF)’ or ‘GPS11 (IOP + VF)’ are potentially cost-effective when society is willing to pay £30,000 per QALY. The dashed line is illustrative. The screening strategy ‘GPS11d (IOP + VF)’ has the highest net-benefit when the screening uptake is 30% and the annual cost of sight impairment is £30,000. The vertical continuous line at £19,000 cost of sight impairment illustrates that screening is not cost-effective below this value, regardless of the screening uptake. (b) 5% glaucoma prevalence and 17% uptake of current eye care. The dashed line is illustrative. The screening strategy ‘GPS11d (IOP + VF)’ has the highest net-benefit for screening attendance of 40% and annual cost of sight impairment just above £4500. The vertical continuous line at £3000 cost of sight impairment illustrates that screening by any pathway is not cost-effective below this value, regardless of screening uptake. (c) 1% glaucoma prevalence rate and 6.5% uptake of current eye care. The dashed line is illustrative. The screening strategy ‘GPS11d (IOP + VF)’ having the highest net-benefit for screening attendance of 40% and annual cost of sight impairment above £18,000. IOP: intraocular pressure; GPS: Glaucoma screening Platform Study; QALY: quality adjusted life years; VF: visual field.

Figure 2.

Average expected value of perfect information (EVPI) and expected value of parameter perfect information (EVPPI). Scenario: model start age (and screening) 50 years old, prevalence rate 5%, screening every 10 years, whole population, current practice annual eye test uptake rate 7.4%, average annual cost of sight impairment £20,500. The upper and lower bounds limits for this distribution were informed by the literature,^, assuming that NHS treatment as well as PSS cost were included. Incremental cost-effectiveness ratio for moving to screening (GPS1d (IOP + VF) = £21,720). The peak in EVPI corresponds to the uncertainty in the decision of changing from current practice (opportunistic case finding) to screening with a technician conducting tonometry and visual field test (perimetry) with screen positives examined by a specialized optometrist (GPS11d (IOP + VF)). EVPPI shown for selected parameters that contributed the most to decision uncertainty. IOP: intraocular pressure; GPS: Glaucoma screening Platform Study; PSS: personal social services; VF: visual field.