What is the difference between qaly and daly

QALYs can lack sensitivity and may be difficult to apply to chronic disease and preventative treatment. Disease-specific measures may be used, but must be interpreted with caution. Lastly, social preference weighting and discounting of DALYs present certain ethical issues: are young adults and non-disabled more productive and valuable to society?

Does the value of health decrease over time? QALYs and DALYs are tools, providing a single measure of mortality and morbidity, used internationally for assessing health care interventions and treatments. Their application in the realm of Public Health enables policy makers to make informed decisions, and countries to choose vital, cost-effective health solutions.

Introduction Average life expectancy has increased but are these additional years healthy, productive and enjoyable? Conclusion QALYs and DALYs are tools, providing a single measure of mortality and morbidity, used internationally for assessing health care interventions and treatments. Health Policy Plan 21 5 Health economics 2nd edition. World Health Organization. The Global Burden of Disease concept. Disability-adjusted life years: A critical review.

Systematic differences between QALYs and DALYs are explained by reference to two examples: the prevention of tuberculosis and the treatment of bipolar depression. When a health intervention is aimed at preventing or treating a non-fatal disease, the relationship between QALYs gained and DALYs saved depends on age of onset and duration of the disease, as well as the quality of life and disability weights.

In the case of a potentially fatal disease, a larger number of factors may determine differences between outcomes assessed with the two metrics. The relative importance of some of these factors is discussed and illustrated graphically in the paper. Understanding similarities and differences between QALYs and DALYs is important to researchers and policy makers, for a sound interpretation of the evidence on the outcomes of health interventions.

Early applications of the health status index include one on tuberculin screening Bush et al. These conditions and the utility theory foundations of QALYs were further discussed in a number of contributions, including those of Myamoto and Eraker , Loomes and McKenzie , Mehrez and Gafni An extensive review published in counted 51 economic evaluations using QALYs as the outcome measure Gerard Only a few years later the QALY framework was widely accepted as the reference standard in cost-effectiveness analysis Gold et al.

Bleichrodt and Johannesson Today, QALYs are used in most economic evaluations, and by many regulatory agencies which have made cost-effectiveness analysis an integral part of their decision-making processes. The QALY framework provided a basis for the development of a number of health outcome measures, including the disability-adjusted life year DALY in the early s.

The DALY is primarily a measure of disease burden disability weights measure loss of functioning but its use in cost-effectiveness analysis is also relatively common, and this paper is concerned with the latter. Most importantly, the DALY incorporates an age-weighting function assigning different weights to life years lived at different ages, and the origins of disability and quality of life weights differ significantly. Although the disability profiles upon which DALY calculations are based tend to be simple e.

On the other hand, quality of life profiles or health profiles for QALY calculations tend to be more elaborate, allowing for sequential upward or downward health status changes over time, but the corresponding calculation methods can be made less cumbersome by using a discrete approximation of a continuous health function Drummond et al.

This paper illustrates the methods for calculating QALYs, providing formulas that can be applied directly by researchers, similar to those made available elsewhere for DALY calculations. This paper is about calculation methods, and it does not aim at providing a comprehensive discussion of the conceptual and methodological differences between the two measures, which are well documented in other contributions.

In particular, Broome provides a detailed discussion of the conceptual framework of QALYs, while methods for eliciting health state utility values are presented in Torrance Most of the challenges to the QALY framework have been based on the difficulties involved in making interpersonal comparisons and aggregating individual utilities; the assumptions on which health utility elicitation methods are based; and the implicit discrimination against the elderly and the chronically ill or disabled.

Key challenges to the DALY framework have focused on the equity implications of age-weighting and of the standard life expectancy assumption used in cross-country comparisons, but also on the methods used to assess disability weights. A direct comparison of the two measures is presented in Gold et al.

Although measured on similar scales, the former represent levels of quality of life enjoyed by individuals in particular health states, while the latter represent levels of loss of functioning caused by diseases. The former are normally measured on a scale in which 1 represents full health and 0 represents death, therefore higher values correspond to more desirable states and states deemed worse than death can take negative values.

The latter are measured on a scale in which 0 represents no disability, therefore lower scores correspond to more desirable states. The two types of weights are also derived in different ways, using different elicitation techniques and different groups of subjects. In practice, DALY calculations tend to be based on a universal set of standard weights based on expert valuations, while QALY calculations often rely on preference-based health-related quality of life measures directly elicited from general population samples or from groups of patients.

The most common preference elicitation techniques are the standard gamble and the time trade-off, both choice-based Torrance These may be applied directly, or indirectly in the assessment of the value of individual dimensions of multi-attribute systems like the Health Utilities Index Torrance et al.

Health profiles with constant quality of life. Note : Health profiles with intervention i solid line , and without intervention broken line. Health profiles with variable quality of life. The calculation methods illustrated in the previous section will be applied in two examples, one on tuberculosis, a temporary non-fatal disease, and one on bipolar disorder, a chronic disease potentially affecting life expectancy.

In both examples, it is initially assumed that the loss of quality of life determined by the respective diseases in QALY calculations is exactly equivalent to the level of disability estimated in DALY calculations i. This assumption will be later relaxed to illustrate the impact of potential differences between the two.

Finally, quality of life is assumed stable throughout the duration of the disease. An individual affected by tuberculosis will experience a temporary, non-fatal disability if the disease is appropriately diagnosed and treated. The level of disability attributed to tuberculosis in the GBD study varies in a relatively narrow range 0. Dion et al. Therefore, it is not possible to calculate conversion factors like those reported in Table 1.

Tsevat et al. Figures 4—6 illustrate how QALYs gained and DALYs saved vary in relation to changes in, respectively, age of disease onset a , duration of disability without treatment L , and disability weight with treatment D i. Benefits of preventing a potentially fatal disease: effect of age of disease onset a. Benefits of preventing a potentially fatal disease: effect of duration of disability without treatment L.

Benefits of preventing a potentially fatal disease: effect of disability weight with treatment D i. This paper provides an illustration of calculation methods for assessing quality-adjusted life expectancy and for measuring the outcomes of health interventions in terms of QALYs. Two examples in different disease areas have shown that age of disease onset is an important factor determining variations between numbers of QALYs gained and DALYs saved, when interventions are compared using the two metrics.

The pattern of variation is mostly dictated by the shape of the age-weighting function. These conclusions are based on the use of the age-weighting function originally proposed in the GBD study Murray and Lopez , still most widely applied in DALY calculations.

QALY is usually used in measuring the quality and quantity of care and life when considering options for health treatments for a particular illness. In measurements, both DALY and QALY only produce a single number either 1 or 0 to express death or perfect health in the extension of describing the quality and quantity of health.

QALY measures the burden of disease on a life with the inclusion of quality and quantity of lived life. It is a method of evaluation that offers information in considering, measuring, and choosing health interventions often in the role of disease treatment.

It generates an estimated number of years that can be added to a life if an intervention is given. Another field that it considers is the financial costs of the medical intervention. Factors in measuring the quality of life that are to considered in QALY are: degree of pain, mobility, and general mood.

QALY is expressed in either 1. In contrast, DALY measures mortality and mobility. In a sense, it is a modified version of QALY. It deals with the years lost due to the poor quality of life due to illness and disability or any non-lethal heath problem or lifetime lost due to an early death. DALY places consideration on disability, discounting, and age. Quality adjusted life years and disability adjusted life years are both measurements to calculate the quality and quantity of life either of individuals or the general population.

Both evaluations have different coverage and interpretations.