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Measuring quality of life after injury
  1. Ronan Lyons
  1. Correspondence to Professor Ronan Lyons, School of Medicine, Grove Building, Swansea University, Swansea SA2 8PP, UK; r.a.lyons{at}swansea.ac.uk

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Injuries often result in a series of negative consequences for individuals, their families, close friends and wider society.1 Quality of life, or more specifically health-related quality of life, after injury is essentially a summary measure of the health impact of non-fatal injuries on individuals. It is most commonly measured using multi-attribute utility instruments (MAUIs), such as the EuroQol-5D (EQ-5D) or the Health Utility Index (HUI2, HUI3).2 3

MAUIs are standardised health-state classifications which can be used to produce a single utility score based on individuals' responses to questions on the impact of health conditions or injuries on their lives and the preferences of the general public for different health states. The utility scores are designed to range from 0 to 1, and together with information on the duration of health states are used to produce the ‘years lived with disability’ component of disability-adjusted life years (DALYs).4

There are two different approaches to calculating DALYs for injuries. One approach is to use panels of people to provide relative valuations of different health states based on a limited number of vignettes or idealised case descriptors—for example, the Global Burden of Diseases, Injuries and Risk Factors (GBD) Study or the Dutch Burden of Injuries Group.5 6 The alternative approach is to use MAUIs in large empirical studies of injured individuals. There are surprisingly few studies of either type in the literature, and there is considerable debate as to which approach is most valid. When the MAUI approach is used, there is a choice between instruments, but little guidance. A literature review and theoretical comparison of the derivation and content of instruments recommended that EQ-5D and HUI3 be used in combination for studying injury-related disability.7 However, it remained uncertain as to what the theoretical benefit of using both instruments would be in practice. In this issue of the journal, Polinder et al8 tested the benefits of the combined approach by using the EQ-5D, HUI2 and HUI3 in a follow-up study of 1454 Dutch people who had attended an emergency department with an injury diagnosis 2 years previously (see page 147). They found that, while the EQ-5D had slightly lower average summary scores (0.78) than the HUI3 (0.80), and substantially lower scores than the HUI2 (0.88), the HUI3 was somewhat more responsive to ageing, comorbidity, and perhaps lower-extremity injuries.8 The authors concluded that, although the different MAUIs resulted in significantly different summary scores, there was still benefit in combining the two instruments in studies of injury-related disability. Given the theoretical benefits of the HUI3 over the EQ-5D, in part due to 972 000 possible health-state permutations from 15 questions compared with 243 from five questions, the results show surprisingly little difference in overall scores. Differences between summary scores for specific injury groups did not show a consistent pattern favouring one instrument over the other, and these were not tested for statistical significance.

Given that the difference between instruments was small and that the HUI3 requires payment of a fee and was also associated with lower completion rates (82% vs 88%), the EQ-5D may have considerable practical advantages in terms of logistics and cost for those planning studies in less resourced environments.

There are few empirical or panel studies that measure the disability component of the burden of injuries. The 1990 GBD Study, which produced population estimates of the burden of injuries, is currently being revised, with 2005-based estimates due in 2010.5 The process of producing the revision is well underway and is being assisted by a number of expert panels, including the Global Burden of Diseases Injury Expert Group.9 10 One of the problems with the existing studies is the use of combined disability weights and durations for quite heterogeneous groups of injuries. This is due, in part, to the difficulty of finding funding to support large-scale studies of post-injury disability; consequently, most empirical studies have grouped injuries into relatively few categories. Panel studies are also limited by the number of case vignettes that can be considered by participants. The UK Burden of Injuries Study compared the different injured groupings available and the proportion of injury cases from emergency department and hospital discharge surveillance systems that could be mapped to the different groups.11 The 13-category group used by Dutch researchers faired best with 91% of emergency department and 87% of hospital discharge cases being coded to specific groups, compared with 67% and 78% for the GBD Study, and 66% and 58% for the alternative Dutch panel study.12 5 6

Given the scarcity of studies with empirical data, there is a clear need to improve upon injury disability metrics by combining data from studies using MAUIs or other health-related quality of life measures. This thinking has led to the International Collaborative Effort on Injury Statistics (ICE) initiating a project with the following aims: to identify key injury studies with empirical data from around the world covering a wide variety of severities and treatment settings; to establish the relationship between disability metrics from different instruments in order to combine data across studies; to explore novel injury grouping strategies that reflect the influence of injury patterns on disability; and to validate the 2005 Global Burden of Diseases injury-specific disability weights.13 Those interested in contributing to the ICE project should contact Belinda.Gabbe{at}med.monash.edu.au. The Polinder et al study8 will also contribute to this initiative by providing metrics for the comparison of studies using the EQ-5D or HUI3.2 3 The overall result will be an improvement in the methods used to measure the burden of injury.

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  • Competing interests None.

  • Provenance and peer review Commissioned; not externally peer reviewed.

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