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Quality-Adjusted Life Years or QALYs means measuring disease burden, including both the QOL, quantity of life lived and Compression Of Morbidity, as a means of quantifying the benefit of a medical or Preventive Health intervention.  The QALY model requires utility independent, risk neutral, and constant proportional trade-off behaviour.

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 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 be confined to a wheelchair, then the extra life-years are given a value between 0 and 1 to account for this.

Another way of determining the weight associated with a particular health state is to use standard descriptive systems such as the EuroQol EQ-5D questionnaire, which categorise 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 QOL, compared to those who are afflicted.

QALYs are used in cost-utility analyses 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 ratio being preferred over an intervention with a higher ratio. This method is controversial because it means that some people will not receive treatment as it is calculated that cost of the intervention is not warranted by the benefit to their QOL.  However, its supporters argue that since health care resources are inevitably limited, this method enables them to be allocated in the way that is most beneficial to society.

Basically QALY takes one year of perfect health-life expectancy to be worth 1, but regards one year of less than perfect life expectancy as less than 1.  Thus an intervention which results in a patient living for an additional four years rather than dying within one year, but where quality of life fell from 1 to 0.6 on the continuum will generate:

  1. 4 years extra life @ 0.6 quality of life values 2.4

  2. less 1 year @ reduced quality (1 - 0.6) 0.4
  3. QALYs generated by the intervention 2.0

QALYs can therefore provide an indication of the benefits gained from a variety of interventions in terms of QOL and survival for the patient.  Another example is shown in the figure, where treatment provides a higher area under the QALY/time curve than does no treatment.

 

See also Transfer To Utility or TTU and Section 18(a).

Also referred to in Section 18 and Why YELP is a Business Plan and not solely a Research Programme, and definitions of Health Assessment Appointment,  Primary Research Programme Brief,  Economic Return On YELP Capex,  Return On YELP Capex Software,  Head Consultant's Conditions Precedent To The Pilot,  Initial Lifestyle Behaviour Evaluation Of Each Volunteer.