The clinical effectiveness and cost-effectiveness of screening programmes for amblyopia and strabismus in children up to the age of 4-5 years: a systematic review and economic evaluation

Abstract

To estimate the cost-effectiveness of screening for amblyopia and strabismus in children aged up to 4-5 years, also identifying the major areas of uncertainty and so inform future research priorities in this disease area. Major electronic databases were searched in January 2006. Systematic literature reviews were undertaken to determine the prevalence and natural history, the screening methods, the effectiveness of treatment options and health-related quality of life issues relating to amblyopia and strabismus. The review of treatment interventions was restricted to high-quality reviews, meta-analyses and guidelines. The data derived from the review informed the structure and implementation of the decision-analytic model. The amblyopia screening model was analysed in detail to estimate the cost and effects of six alternative screening options comprising screening at different ages (3, 4 and 5 years) and using alternative sets of tests (visual acuity testing and the cover tests, with and without autorefraction). The reference case results showed that screening programmes that included autorefraction dominated screening programmes without autorefraction. Analyses based on the cost per case of amblyopia prevented showed screening at either 3 or 4 years prevented additional cases at a low absolute cost (3000-6000 pounds sterling). However, when these results were extrapolated to estimate the cost per quality-adjusted life-year (QALY) gained, the reference case analysis found that no form of screening is likely to be cost-effective at currently accepted values of a QALY. The wide-ranging sensitivity analyses found that the results were robust to most parameter changes. The only parameter that radically affected the results was the utility effect of loss of vision in one eye. No direct evidence of a utility effect was identified and the reference case assumed no effect. When a small effect is assumed (a reduction in utility of 2%), the incremental cost per QALY gained becomes extremely attractive for screening at both 3 and at 4 years. The expected value of perfect information was shown to be large when the unilateral vision loss utility parameter was allowed to vary, but not when it was kept constant at zero. The results show that the cost-effectiveness of screening for amblyopia is dependent on the long-term utility effects of unilateral vision loss. There is limited evidence on any such effect, although our subjective interpretation of the available literature is that the utility effects are likely to be minimal. Any utility study investigating such effects would need to be careful to avoid introducing bias. The reference case model did not represent potential treatment-related utility effects, primarily due to an increased probability of treated children being bullied at school. The evidence indicates that this may be a problem, and additional sensitivity analyses show that small utility decrements from bullying would improve the cost-effectiveness of early screening significantly. A prospective study of the utility effects of bullying would usefully inform the analysis, although such a study would need to be carefully planned in order to distinguish whether the overall incidence of bullying decreases with reduced school-age treatment, or whether it is displaced to other children.