Quality of Well-Being Scale

Health-Related Quality of Life

HRQOL describes a comprehensive picture of health and overall well-being. HRQOL measures differ from one another along several dimensions, including generic versus disease-specific measures and psychometrically based versus preference-based measures. The QWB is a generic measure in that it was designed to be used with any adult population and any health condition, including healthy individuals. The QWB is a preference based measure and was not developed to assess statistically independent domains of HRQOL. It is preference based, meaning that it is scored on the basis of mean health consumer preferences or utilities for the health states. These preferences or utilities are the ratings of observable health states using a continuum anchored by death and optimum health.

Quality of Well-Being

The QWB was developed in the 1970s using theory from the general health policy model. This model includes several components, including mortality (death) and morbidity (HRQOL). The theory proposes that symptoms and disabilities are important for two reasons: First, illness may cause life expectancy to be shortened and, second, illness may make life less desirable at times prior to death. In assessing the impact of a health intervention, the model requires data on both a possible change in mortality as well as a change in HRQOL. In addition to mortality and morbidity, the general health policy model incorporates preference for observed health states (utility) and duration of stay in health states. Preferences or utility for health states are typically measured using economic principles that ask individuals to prioritize or place values on a wide variety of health states involving both symptoms and functioning. The health [Page 873]preferences or utilities are placed on a preference continuum for the desirability of various health states, giving a ‘quality’ rating on an interval scale ranging from 0 = death to 1.0 = completely well.

Calculation

Once a value is obtained that describes the level of morbidity or wellness in a sample using a measure such as the QWB, the score can be multiplied by the amount of time at that level of wellness to calculate QALYs. A QALY is defined as the equivalent of a completely well year of life, or a year of life with optimal functioning and no health problems or symptoms. Consider, for example, a person who has a set of symptoms and is in a state of functioning that is rated by community peers as 0.5 on a 0.0 to 1.0 scale. If the person remains in that state for 1 year, he or she would have lost the equivalent of 1/2 of 1 year of life. Thus, a person limited in activities who requires a cane or walker to get around the community would be hypothetically rated at 0.50. If he or she remained in that state for an entire year, the individual would lose the equivalent of one-half year of life. However, a person who has the flu may also be rated as 0.50. In this case, the illness might only last 3 days and the total loss in QALYs might be 3/365 × 0.50, which is equal to 0.004 QALYs. This may not appear as significant an outcome as noted for the disabled person. But suppose that 5,000 people in a community get the flu. The well years lost would then be 5,000 × 0.004, which is equal to 20 years of perfect health in one person. An important feature of the system is that it is completely generic. It can be used to compare small health consequences that affect a large number of people with large health consequences that affect a small number of people. The quality-adjusted life expectancy is the current life expectancy adjusted for diminished quality of life associated with dysfunctional states and the duration of stay in each state.

...