Читать книгу Clinical Pharmacology and Therapeutics - Группа авторов - Страница 147

It is helpful to use an example to explain why CUA is such a useful form of economic evaluation.

In cardiovascular disease, there are many different treatments available and each treatment will give rise to a specific pattern of costs and effects. For example, in seeking to manage a patient's weight, clinicians could use lifestyle interventions or drug therapy. If drug therapy provided greater benefits but at an increased cost compared with lifestyle modification, then economic evaluation can provide a marker to help the decision maker judge whether the additional costs are justified by the additional benefits. In comparing two (or more) treatment options in an economic evaluation, the convention is to calculate the additional benefit provided by the more effective treatment and then present the findings in terms of ‘cost per additional unit of benefit’, e.g. ‘cost per additional life year gained’. Frequently, treatments offer a range of effects such as an improvement in symptoms and better survival. CEA using an outcome measure such as a ‘cost per additional life year gained’ would struggle to take account of both dimensions of benefit.

QALYs have the advantage of being able to capture gains in quality of life and quantity of life (=survival) in a single measure. The QALY adjusts length of life for quality of life by assigning a value (known as a utility value) between 0 and 1 (where 0 represents death or health states considered as bad as being dead and 1 represents perfect health) for each year of life. Negative utility values are also possible for some conditions that are considered to be worse than being dead, such as the end stage of a degenerative illness. Figure 3.1 illustrates the concept of a QALY. Without the new health technology, the individual's quality of life, measured on the y axis, would deteriorate over time until they die (‘Death 1’). However, with the new technology, the individual's quality of life is maintained at a higher level until they die, a few years later than they would have done with the original treatment (‘Death 2’). Area A represents the quality of life gain with the new treatment while area B corresponds to the survival gain with the treatment. Added together, they represent the total QALY gain associated with the new treatment.

Figure 3.1 The concept of quality‐adjusted life year (QALY).