It was found that individual preferences over health are influenced by the duration of health states and their sequence .
However , although there is much variation across individual respondents , the assumptions tend to hold much better when valuations are aggregated across respondents , which is encouraging for economic evaluations that rely on using average ( mean or median ) values
The numbers of quality -adjusted life years ( QALYs ) gained are increasingly being used to represent the gains in individual utility from treatment .
This requires that the value of a health improvement to an individual is a simple product of gains in quality of life and length of life .
The article reports on a systematic review of the literature on 2 issues : whether the value of a state is affected by how long the state lasts , and by states that come before or after it .
Proportional Heuristics in Time Tradeoff and Conjoint Measurement
The time-tradeoff ( TTO ) test is widely used to measure quality of life for different health states . Subjects are asked to equate the value of living a given period in an inferior health state to the value of living a shorter period in good health . Applications of TTOs have been criticized based on the fact that the value of future life duration is taken as the future life duration itself . The authors show that for a health state in which a subject does not want to live longer than a specified amount of time , subjects ' responses do not comply with the assumption that the value of the period in inferior health is equated to the value of the shorter period in good health Actually , preference reversals with respect to such a health state point to the use of a proportional heuristic in the TTO test . Comparisons of the TTO test in these subjects with category scaling and difference measurements also favor a proportional inter pretation of the TTO test . In tests based on conjoint measurement , these subjects also appear to use a proportional heuristic . Consequences of the use of the TTO test and conjoint measurement m quality -of-life models are discussed Key words : utility assessment , QALY , conjoint measurement ; preference reversals ; compatibility effect . ( Med Decis Making 1996;16:36 - 44
It was found that individual preferences over health are influenced by the duration of health states and their sequence .
However , although there is much variation across individual respondents , the assumptions tend to hold much better when valuations are aggregated across respondents , which is encouraging for economic evaluations that rely on using average ( mean or median ) values
The numbers of quality -adjusted life years ( QALYs ) gained are increasingly being used to represent the gains in individual utility from treatment .
This requires that the value of a health improvement to an individual is a simple product of gains in quality of life and length of life .
The article reports on a systematic review of the literature on 2 issues : whether the value of a state is affected by how long the state lasts , and by states that come before or after it .