Sexually Transmitted Diseases:
Health Utility Measures for Pelvic Inflammatory Disease
Gift, Thomas L. PhD
From the Centers for Disease Control and Prevention, Atlanta, Georgia
The findings and conclusions in this manuscript have not been formally disseminated by the CDC and should not be construed to represent any agency determination or policy.
Correspondence: Thomas L. Gift, PhD, Centers for Disease Control and Prevention, 1600 Clifton Rd. NE, Mail Stop E-80, Atlanta, GA 30333. E-mail: email@example.com.
Received for publication December 10, 2007, and accepted December 16, 2007.
HEALTH UTILITY MEASURES are an important tool in economic analyses of health because they use a single standard to quantitatively value the utility associated with a given health state or disease. They measure the gap between perfect health (usually scored as 1 or 100) and death (typically scored as 0), and address a variety of dimensions of health, including physical functioning, social functioning, and perception of well-being.1 Combining these quantitative values with their duration leads to measures of health such as disability-adjusted life years (DALYs) or quality-adjusted life years (QALYs).2 These common units allow interventions aimed at different health conditions to be compared in terms of cost-effectiveness; analyses using QALYs or DALYs are usually referred to as cost-utility analyses.3,4
Resource allocation questions often occur at a level above that of a single clinic, which might only face choices confined to optimizing care for a particular infection or related infections. An STD clinic manager might need to decide whether to screen all women or only women under the age of 25 years for chlamydia. For this question, an analysis comparing cost per case of chlamydia treated is adequate. However, a health plan manager or director of a state department of health might need to know whether to increase funding for chlamydia screening in young women, expand vaccination programs aimed at children, or screen adults routinely for hearing loss. Having a common unit of measure of the health benefit achievable by each intervention is essential for this kind of decision making. Cost-utility analysis is a tool that can provide information to aid decision makers in balancing such diverse competing needs.5
The work of Smith and colleagues in this issue makes an important contribution to the measurement of the health burden associated with pelvic inflammatory disease (PID) and its sequelae.6 It joins previous work on the subject. An earlier study used data from the 1987–1992 National Health Interview Survey (NHIS) to estimate the health utility of persons with PID7; a more recent effort estimated the utility impact of PID and its sequelae based on estimates by an expert panel.8 These estimates have been used in analyses of chlamydia screening.9–11
Although it is clear that health utility measures are useful, estimating them is not necessarily an easy process. There are several available indices that assign health utility values to various health states; these can be matched to those experienced by PID patients as closely as possible, or data can be collected directly from individuals to generate utility estimates.12 Smith and colleagues used 2 tools to value the health states associated with PID and its sequelae, a visual analogue scale (VAS) and a time trade-off (TTO) valuation.6 The VAS is a simple way to indicate the relative reduction in health imposed by a condition, but this simplicity makes it less well-accepted in cost-utility analysis than other methods.13 With time trade-off valuation, people are asked to make an explicit choice between living for a longer time with the given health condition or living in better health without the condition for a shorter period of time.14 Nonetheless, there is theoretical support for VAS use.15 Smith and colleagues make a significant contribution by obtaining PID health state valuations from 2 groups of women—those who reported a history of PID and those who did not. This enabled them to compare the valuations that the 2 groups assigned to each state for significant differences, and to compare both groups’ responses to utility values previously generated by an expert panel.8 As Smith and colleagues note, health state valuations from the general public are generally recommended for use for societal-level analyses,4 but when differences in valuations between the general public and those who have experienced a health state exist, they pose important questions for analyses from patient and societal perspectives.16 A second contribution by Smith and colleagues is that they made it possible to compare health state valuations using TTO and VAS.
Smith and colleagues found that patients attributed substantial disutility to health states associated with PID. They discovered that patients with a history of PID attributed significantly more disutility to pelvic pain, infertility, and ectopic pregnancy than women who had no PID history when using VAS but not when using TTO. The patients’ values for the health states were similar to or somewhat lower than those estimated by the expert panel.8 They provide empirical validation of that panel’s work.
These findings do not themselves constitute a cost-utility analysis for various interventions aimed at PID prevention, but they provide measures that can be used by analyses that also incorporate cost and preventable burden estimates. They will improve cost-utility analyses of interventions aimed at preventing chlamydia and gonorrhea. Refining health utility measures for additional STD-related syndromes and sequelae will provide estimates needed to comprehensively evaluate and properly target resources needed for STD prevention and highlight how cost-effective STD interventions can be.
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