Elsevier

The Lancet

Volume 354, Issue 9173, 10 July 1999, Pages 111-115
The Lancet

Articles
Multiple-informant ranking of the disabling effects of different health conditions in 14 countries

https://doi.org/10.1016/S0140-6736(98)07507-2Get rights and content

Summary

Background

The Global Burden of Disease study provided international statistics on the burden of diseases, combining mortality and disability, that can be used for priority setting and policy making. However, there are concerns about the universality of the disability weights used. We undertook a study to investigate the stability of such weighting in different countries and informant groups.

Methods

241 key informants (health professionals, policy makers, people with disabilities, and their carers) from 14 countries were asked to rank 17 health conditions from most disabling to least disabling. Kruskal-Wallis ANOVA was used to test for differences in ranking between countries or informant groups and Kendall τ-B correlations to measure association between different rank orders.

Findings

For 13 of 17 health conditions, there were significant (p<0·05) differences in ranking between countries; in the comparison of informant groups, there were significant differences for five of the 17 health conditions. The overall rank order in the present study was, however, almost identical to the ranking of the Global Burden of Disease study, which used a different method. Most of the rank correlations between countries were between 0·50 and 0·70 (average 0·61 [95% CI 0·59–0·64]). The average correlation of rank orders between different informant groups was 0·76.

Interpretation

Rank order of disabling effects of health conditions is relatively stable across countries, informant groups, and methods. However, the differences are large enough to cast doubt on the assumption of universality of experts' judgments about disability weights. Further studies are needed because disability weights are central to the calculation of disability-adjusted life years.

Introduction

The Global Burden of Disease study1 has attracted the attention of policy makers and public-health experts because the study provides a common unit for evaluation and priority setting for a wide range of health disorders. This unit, the disability-adjusted life year (DALY), adds disability to mortality in the overall estimation of the burden of disease. The addition of disability has increased the relative importance of non-communicable diseases, and the result is a more realistic measure of the global burden of diseases than that obtained from mortality alone.2, 3 DALYs provide a framework for different professions in determining priorities in health and human services and in evaluating the efficacy of interventions since they are based on life years, a universal measure.3 Policy makers have a particular interest in making decisions on resource allocation and policy, and monitoring the impact of health-care reforms and other interventions with a common measure applicable in cost-effectiveness studies. The DALY is useful because it provides a common measure by making valid epidemiological data usable in an internally consistent approach.4

There have been various attempts to develop composite health measures that combine information on mortality and non-fatal health outcomes to represent population health in a single number.5 One of the most widely adopted methods uses the quality-adjusted life years (QALY) model.6, 7 This model attempts to measure the impact of a disease in terms of different combinations of duration and quality of life.8 DALY is the complement to QALY, the disability weight being the reverse scale of quality of life. Healthy life years (HALYs) and health-adjusted life years (HALYs) are other methods used to measure burden of disease.9 The cross-cultural applicability of these methods and the equivalence of derived preferences have not been standardised globally, regionally, or nationally.

Although DALYs improve our understanding of international health statistics and can influence the policy process through decisions on resource allocation, great care must be taken in their construction, which involves choices and value judgments.5 There is great concern that the calculation of the disability component in DALYs is based principally on disease-specific disability weights that indicate values for less than perfect health. That is, a perfectly healthy state has a weight of 0, and death is equivalent to a weight of 1. Hence, disease-related disability is placed between these endpoints: for example, angina has a weight of 0·223, major unipolar depression 0·619, and quadriplegia 0·895.1 In the Global Burden of Disease study these weights were determined with professional health-care providers through the person trade-off method.10 Professional health-care providers were chosen because they are familiar with health conditions and their outcomes, and such familiarity makes it easier to form the often complex comparisons between the impacts of different disease states required by the person trade-off protocol.

Professional health-care providers were assumed to be representative of society's preferences with regard to resource allocations in health care. This assumption, however, requires empirical support, and for empirical testing, preference measures should also be obtained from various other groups such as policy makers and individuals with disabilities to see how these measures converge.

Furthermore, these disability weights are presumed to be universal, that is, equal across countries and cultures. Yet they were in fact derived from a single person trade-off exercise carried out at the WHO in Geneva. Although the results of other exercises since then suggest similar results,1 there is a clear need for more systematic testing across different cultures and different informant groups with other forms of measurement. This study was motivated by these concerns about the universality of the disability weights used in the construction of DALYs.

In a large study on the cross-cultural applicability of a proposed revision of the International Classification of Impairments, Disabilities and Handicaps,11, 12 a sub-study examined whether expert ratings on the disability effects of different health conditions were universal, in the sense of being stable across methods, cultures, and informant groups. Ranking was the chosen method rather than the person trade-off method because ranking requires less specialised participants, less time, and no technical knowledge. The original Global Burden of Disease study protocol also used an ordinal ranking exercise in addition to a variant of the person trade-off protocol, and required respondents to reconcile the discrepancies between the two during a deliberative phase.1 Our study attempted to replicate independently the results of the exercise carried out within the framework of the Global Burden of Disease study in different cultures with different informants. We should point out, however, that because of the difference in methods, our study can only test the assumptions of the Global Burden of Disease study (eg, stability of disablement scores across cultures and informant groups). With the ranking exercise, disability weights cannot be derived. The choice of method is justified since the main aim of our study is to test the underlying assumptions of the Global Burden of Disease study. Ranking exercise also requires much less time (10–15 min instead of 2 days per group for the person trade-off method).

We aimed to answer four questions. Are there significant differences in the ranking of the disabling health conditions by key informants from different countries? Are there significant differences in the ranking of the disabling health conditions by respondents from different informant groups (medical professionals, allied health professionals, health-policy makers, consumers, or caregivers)? Could the ranking of the disability weights of the Global Burden of Disease study be replicated with a different method? What are the underlying patterns in respondent ratings of disabling effects of health conditions?

Section snippets

Participants

Informants from 14 countries took part in this study (Canada, China, Egypt, Greece, India, Japan, Luxembourg, the Netherlands, Nigeria, Romania, Spain, Tunisia, Turkey, and the UK). Thus, all WHO regions were represented in the study.

Key informants were defined as those who, by virtue of their position and knowledge, have an understanding of disabilities that makes them representative spokespersons for their culture. For each country, 15 informants were selected—three individuals from each of

Results

Interview data were collated, and the 17 health conditions were ranked from most disabling to least disabling (table 1). Overall, the ranking of the conditions at both ends of the range showed less variability between informants than that for intermediate conditions.

There were, however, deviations from this order across countries (table 2). Active psychosis was ranked most disabling in the Netherlands and Canada but third overall. HIV infection was given a low ranking by informants from Japan,

Discussion

Although there was some variation, the rankings of the disabling effect of health conditions are stable across countries and informant groups, irrespective of the method used for the ranking, as shown by the high correlations between the Global Burden of Disease study and this study, and the close agreement among the 14 countries and among the eight informant groups in our study. Thus, the responses from the key informants show that the relative burden of different health conditions, in terms

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