Quality-adjusted life years
Encyclopedia
The quality-adjusted life year (QALY) is a measure of disease burden, including both the quality and the quantity of life lived. It is used in assessing the value for money of a medical intervention. The QALY model requires utility independent
, risk neutral
, and constant proportional tradeoff behaviour.
The QALY is based on the number of years of life that would be added by the intervention. Each year in perfect health is assigned the value of 1.0 down to a value of 0.0 for death. If the extra years would not be lived in full health, for example if the patient would lose a limb, or be blind or have to use a wheelchair
, then the extra life-years are given a value between 0 and 1 to account for this.
to calculate the ratio of cost to QALYs saved for a particular health care intervention. This is then used to allocate healthcare
resources, with an intervention with a lower cost to QALY saved (incremental cost effectiveness) ratio ("ICER") being preferred over an intervention with a higher ratio.
Another way of determining the weight associated with a particular health state is to use standard descriptive systems such as the EuroQol Group's EQ5D questionnaire, which categorises health states according to the following dimensions: mobility, self-care, usual activities (e.g. work, study, homework or leisure activities), pain/discomfort and anxiety/depression.
However, the weight assigned to a particular condition can vary greatly, depending on the population being surveyed. Those who do not suffer from the affliction in question will, on average, overestimate the detrimental effect on quality of life, compared to those who are afflicted.
QALYs were invented by two health economists in 1956: Christopher Cundell and Carlos McCartney.
Utility
In economics, utility is a measure of customer satisfaction, referring to the total satisfaction received by a consumer from consuming a good or service....
, risk neutral
Risk neutral
In economics and finance, risk neutral behavior is between risk aversion and risk seeking. If offered either €50 or a 50% chance of each of €100 and nothing, a risk neutral person would have no preference between the two options...
, and constant proportional tradeoff behaviour.
The QALY is based on the number of years of life that would be added by the intervention. Each year in perfect health is assigned the value of 1.0 down to a value of 0.0 for death. If the extra years would not be lived in full health, for example if the patient would lose a limb, or be blind or have to use a wheelchair
Wheelchair
A wheelchair is a chair with wheels, designed to be a replacement for walking. The device comes in variations where it is propelled by motors or by the seated occupant turning the rear wheels by hand. Often there are handles behind the seat for someone else to do the pushing...
, then the extra life-years are given a value between 0 and 1 to account for this.
Use
The QALY is often used in cost-utility analysisCost-utility analysis
Cost–utility analysis is a form of financial analysis used to guide procurement decisions. The most common and well-known application of this analysis is in pharmacoeconomics, especially health technology assessment .-CUA in health economics:...
to calculate the ratio of cost to QALYs saved for a particular health care intervention. This is then used to allocate healthcare
Health care
Health care is the diagnosis, treatment, and prevention of disease, illness, injury, and other physical and mental impairments in humans. Health care is delivered by practitioners in medicine, chiropractic, dentistry, nursing, pharmacy, allied health, and other care providers...
resources, with an intervention with a lower cost to QALY saved (incremental cost effectiveness) ratio ("ICER") being preferred over an intervention with a higher ratio.
Meaning
The meaning and usefulness of the QALY is debated. Perfect health is hard, if not impossible, to define. Some argue that there are health states worse than death, and that therefore there should be negative values possible on the health spectrum (indeed, some health economists have incorporated negative values into calculations). Determining the level of health depends on measures that some argue place disproportionate importance on physical pain or disability over mental health. The effects of a patient's health on the quality of life of others (e.g. caregivers or family) do not figure into these calculations.Weighting
The "weight" values between 0 and 1 are usually determined by methods such as:- Time-trade-offTime-trade-offTime-Trade-Off is a tool used in health economics to help determine the quality of life of a patient or group. The individual will be presented with a set of directions such as:Imagine that you are told that you have 10 years left to live...
(TTO): Respondents are asked to choose between remaining in a state of ill health for a period of time, or being restored to perfect health but having a shorter life expectancy. - Standard gamble (SG): Respondents are asked to choose between remaining in a state of ill health for a period of time, or choosing a medical intervention which has a chance of either restoring them to perfect health, or killing them.
- Visual analogue scaleVisual Analogue ScaleA visual analogue scale is a psychometric response scale which can be used in questionnaires. It is a measurement instrument for subjective characteristics or attitudes that cannot be directly measured. When responding to a VAS item, respondents specify their level of agreement to a statement by...
(VAS): Respondents are asked to rate a state of ill health on a scale from 0 to 100, with 0 representing death and 100 representing perfect health. This method has the advantage of being the easiest to ask, but is the most subjective.
Another way of determining the weight associated with a particular health state is to use standard descriptive systems such as the EuroQol Group's EQ5D questionnaire, which categorises health states according to the following dimensions: mobility, self-care, usual activities (e.g. work, study, homework or leisure activities), pain/discomfort and anxiety/depression.
However, the weight assigned to a particular condition can vary greatly, depending on the population being surveyed. Those who do not suffer from the affliction in question will, on average, overestimate the detrimental effect on quality of life, compared to those who are afflicted.
Debate
The method of ranking interventions on grounds of their cost per QALY gained ratio (or ICER) is controversial because it implies a quasi-utilitarian calculus to determine who will or will not receive treatment. However, its supporters argue that since health care resources are inevitably limited, this method enables them to be allocated in the way that is approximately optimal for society, including most patients. Another concern is that it does not take into account equity issues such as the overall distribution of health states. Also, many would argue that all else being equal, patients with more severe illness should be prioritised over patients with less severe illness if both would get the same absolute increase in utility.QALYs were invented by two health economists in 1956: Christopher Cundell and Carlos McCartney.
See also
- Case mix indexCase Mix IndexCase mix index is the average diagnosis-related group weight for all of a hospital's Medicare volume. It can be used to adjust the average cost per patient for a given hospital relative to the adjusted average cost for other hospitals by dividing the average cost per patient by the hospital's...
- Cost-Effectiveness Analysis RegistryCost-Effectiveness Analysis RegistryThe Cost-Effectiveness Analysis Registry was developed by the Center for the Evaluation of Value and Risk in Health at the Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, Boston, MA. The Registry contains detailed information on over 2,800 cost-utility analyses...
- Cost-utility analysisCost-utility analysisCost–utility analysis is a form of financial analysis used to guide procurement decisions. The most common and well-known application of this analysis is in pharmacoeconomics, especially health technology assessment .-CUA in health economics:...
- Incremental cost-effectiveness ratioIncremental cost-effectiveness ratioThe incremental cost-effectiveness ratio of an intervention in health care is a term used in cost-effectiveness analysis in health economics. It is defined as the ratio of the change in costs of a therapeutic intervention to the change in effects of the intervention.The term does not...
- Disability-adjusted life year (DALY)
- National Institute for Health and Clinical ExcellenceNational Institute for Health and Clinical ExcellenceThe National Institute for Health and Clinical Excellence is a special health authority of the English National Health Service , serving both English NHS and the Welsh NHS...
(United Kingdom) - Quality of lifeQuality of lifeThe term quality of life is used to evaluate the general well-being of individuals and societies. The term is used in a wide range of contexts, including the fields of international development, healthcare, and politics. Quality of life should not be confused with the concept of standard of...
and measurements such as MANSAMANSAMANSA is a scale used to assess quality of life. Its name is short for Manchester Short Assessment of Quality of Life. It was developed by Priebe et al. in 1999. The creators of the scale found the results of the scale to be comparable to the Lancashire Quality of Life Profile.The MANSA consists of...
and Life Quality IndexLife Quality IndexThe Life Quality Index is a compound social indicator of human welfare that reflects the expected length of life in good health and enhancement of the quality of life through access to income...