Measurement of values for states of health with linear analog scales

Abstract

Medical decisions may be greatly influenced by the values that patients place on different states of health. Previous attempts to obtain quantitative estimates of such values have assumed the numerical values assigned to different levels of health will remain constant regardless of the context in which the measurement is made. To examine this assumption, 64 ambulatory patients ranked five scenarios describing different states of health in order of preference. One of the scenarios was ranked as worse than death by 22 percent of raters, and two scenarios were ranked as worse than death by 31 percent of raters. The states were then rated using linear analog scales, first with the anchors or endpoints of perfect health and death, then with the anchor of perfect health replaced by each of the other health states, in descending order of preference, and finally with the anchor of death replaced by each of the other health states, in ascending order of preference. The numerical values assigned to scenarios were substantially and systematically influenced by the anchors on the scale. Relative to the values assigned to health states when anchors of perfect health and death were employed, the same states were assigned systematically higher values when the anchor of death was replaced by other health states, and systematically lower values when the anchor of perfect health was replaced. These findings persisted when states considered worse than death were excluded from the rating process. These results indicate that the quantitative values assigned health states are strongly influenced by the context in which the measurement is made, and that health cannot be regarded as a continuum with death as its lower boundary.