Summarizing Population Health Directions for the Development and Application of Population Metrics (1998) / Chapter Skim
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Appendix C: Mehodological Issues in Measuring Health Status and Health Related Quality of Life for Population Health Measures: A Brief Overview of the
Appendix C: Mehodological Issues in Measuring Health Status and Health Related Quality of Life for Population Health Measures: A Brief Overview of the
Pages 39-57
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From page 39... ...
might be computed to index an individual's lifetime and health prospects. For example, the estimated life expectancy of a 50-year-old male In the United States In 1981 was 25.0 years; In 1993 the estimated life expectancy of a 50-year-old male in the United States was 29.2 years, arid the increase of 4.2 years in life expectancy over the 12-year period gives us information about changes In one of the two aspects of heady and well-being in He United States during that interval.
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by the proportion of the population that was disability-free in that age range in the THIS data. The averaged result was mathematically art early progenitor of health-adjusted life expectancy, where the heals weighting was a O for health states involving disability and ~ otherwise.
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From page 41... ...
This background is discussed at length in a book on costeffectiveness analysis in health and medicine commissioned by the U.S. Public Health Service.9 While the HATE concept was being developed as a descriptive index for health gains in populations, economists, operations researchers, and psychologists were developing the QALY concept for making decisions about which medical treatment or which health system intervention should be undertaken by virtue of its being the most cost-effective.'° ~ ~ The seminal work in this regard is by Fanshel and Bush, who developed a preference-based measure for measuring health in populations, tied it to the foundations of EU decision making for public policy, and then demonstrated its application.C Less than a decade later, the QALY as an outcome measure for cost-effectiveness analysis appeared in He major medical literature.l3 Technically, as a measure of decision outcomes for expected utility decision making, the QALY measure must satisfy some stringent mathematical and psychological properties, as discussed in following sections.
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From page 42... ...
also are meaningful in the same way in that the numerical order of the averages represent better or worse aggregated or prospective heath paths. The most fundamental assumption in the construction of HALY measures is that the part of the measure dealing with weighting health states can be obtained separately from the lifeyears, or time duration part of the measure.
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From page 43... ...
"High-fidelity" health state description systems, able to differentiate thousands or millions of health states that might affect humans, may need to be combined with time measures as if they were fully separable. High-fidelity HALY measures, not relying on the assumption of separability, may well be too complex to allow data collection at a population level.
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From page 44... ...
YHL: Years of Healthy Life is a measure of population health computed experimentally by the U.S. National Center for Health Statistics from data collected in the National Health Interview Survey.5 I will use "YHL" to refer elliptically to the health state weighting component of this measure.
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From page 45... ...
For the most part, these domains cover the descriptive schemes that attempt to generalize across health experiences. Measures that deal only with manifestations of a particular disease or condition may be much more detailed in the aspects of health affected by that disease to the exclusion of aspects not generally affected (for example, measures intended only to describe health states of persons with arthritis may be very detailed about pain and physical function, but generally do not include dimensions dealing with visual ability)
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National Center for Heady StatisticsS and the Medical Outcomes
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From page 47... ...
And by no means are the various combinations considered to be equally likely—so much of the population will probably congregate In a relatively few cells of the classification schemes having many categones. The sheer number of health states does not indicate good or bad on the part of a measure; it is only an indicator of potential for differentiating states of heath.
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From page 48... ...
For the symptom/problem complex, the subject is shown or read a list of possible health conditions (e.g., "general tiredness, weakness, or weight loss," or "trouble learning, remembering, or thinking clearly")
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This pool of questions, or "items" In the jargon, watt cover items ranging from activities that all but the most impaired may be able to do, such as turning over, or toilet~ng, or dressy or bathing oneself, to items about activities only He most physically adept might be able to do such as running long distances or playing vigorous sports. Ideally, if "physical functioning" is a unidunensional concept, all the items can be arranged so that they form a ladder of physical function a person of a given ability would be able to perfonn all tasks from the low end of this ladder up to a certain point, then would not be able to perform any tasks on the ladder above this point.4 Unfortunately, it is difficult to make such a perfect list as there are different aspects of physical functioning, such as fine motor control, flexibility, cardiovascular fitness, strength, for example.
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Assigning numerical weights to health state categories. Once a classification system is set up, the final step is to assign numbers the heal state weights to the different health states that the classification system can distinguish.
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The QWB and the HUT (and thereby the Yew have been developed from broad commun~ty surveys. Members of the community were asked to rate health states and their answers were pooled and analyzed to develop a scoring system that predicts He community-assigned score for each particular health state.
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From page 52... ...
Repeated use of the SG assessment memos will obtain health state utilities for any specified health states. Or, this technique can be used with the separate dunensions to develop art entire scoring Algonquin relating the components of We health state classification system to scores for health states.
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From page 53... ...
how the specific weights are obtained for heal states preference versus nonpreference scaling how to collect preference weights: SG, fro, OR, VA We have established a terminology that helps to distinguish methodological choices: · A Heal Status measure is a system for weighting health states. An example is He SF-36.
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From page 54... ...
In the DALY framework, not only are health states weighted, but there is a weighting of life years that accentuates the concept of dependency of the very young and the very old, in a sense giving more weight to years accumulated in the population during productive adulthood. Although this possibility of weighting life years exists for any QALY measure, the DALY implementation is the only one to date that has incorporated it.
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From page 55... ...
It is a reliable instrument for indicating change in fever status of a patient, and we can probably find that in relevant ranges higher temperatures indicate more uncomfortable health states in most people. But a change from 99°F to 100°F may not at all be the same in subjective discomfort as a change from 102°F to 103°F.
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The utility of different health states as perceived by the general public. Journal of Chronic Diseases 31 :697-704, 1978.
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From page 57... ...
and Klein, BEK. Community-based qu~ity-adjusted life expectancy: Results Tom the Beaver Dam Health Outcomes Study.
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