Cost per QALY

A measure of value for money in cost-utility analysis, calculated as incremental cost divided by the quality-adjusted life years gained relative to a comparator.

Source: Weinstein & Stason 1977

The difference in cost between two options is divided by the difference in quality-adjusted life years they produce, so the figure states what the additional health gained costs relative to the comparator. Both quantities are incremental, and both are discounted where they accrue over time. The comparator must be stated, because the ratio is a property of the comparison rather than of the intervention, and the same treatment assessed against a different alternative produces a different figure.

Source: Weinstein & Stason 1977

It combines length and quality of life into a single measure, weighting each period lived by a value between one, representing full health, and zero, representing a state as bad as being dead, with states worse than dead taking negative values. The weights come from population surveys valuing described health states, so they express societal preferences rather than the judgements of patients or clinicians. A year in a state valued at half therefore counts as half a quality-adjusted life year.

Source: Brazier, Ratcliffe, Salomon & Tsuchiya 2017

A ratio below the threshold indicates that the health gained exceeds the health that would be lost elsewhere when resources are displaced to fund it. On that reasoning the threshold should reflect the health produced by the least productive activity currently funded, which is an empirical property of the system rather than a statement about the value of health. Where the threshold applied is higher than that displacement value, adoption at the threshold removes more health than it adds while each decision appears individually justified.

Source: Claxton et al. 2015

It treats a quality-adjusted life year as equally valuable whoever receives it, so it is silent on whether the recipients are already disadvantaged, how severe their condition was, or how the gains are distributed. Effects on carers and families fall outside standard measures. Aspects of care that matter without changing health status, including dignity and the burden of attending, are not represented in the weights. These omissions are why appraisal frameworks apply additional considerations alongside the ratio rather than deciding on it alone.

Source: Neumann, Sanders et al. 2016

The health state weights depend on the instrument and the valuation method used, so the same intervention yields different ratios under different measures. Preference-based descriptions are insensitive to changes that matter in some conditions, particularly in mental health and sensory impairment. Older people gain fewer quality-adjusted life years from the same intervention because they have fewer years remaining, which some regard as a defensible reflection of benefit and others as discrimination. None of these is resolved, and each is a live dispute rather than a technical detail.

Source: healtheconomics.wiki