In completing the analysis, we applied some simplifying assumptions due to data and time constraints. First, we assumed that the average age of the affected children was 3 years, and that they reflected the same gender distribution as the general population of the same age. Although injuries to a newborn could have quite different effects than would the same injury for a 3- or 6-year-old, the sources used in our analysis did not provide information on age-related HRQL differences for young children. Second, we treated these injuries as if they all occurred in a single year, rather than spread out over a 5-year period. We used discounting only to reflect the time value of averting the future year HRQL impacts associated with an injury that occurs in the current year; we did not discount the different years of incidence in the NASS-CDS data set.
Our assessment of HRQL impacts involved the use of four generic indexes. For two of these indexes, the EQ-5D and the HUI-2, we asked five medical experts to match the characteristics of each injury to the relevant index attributes, following a process similar to that applied in the FDA case study. We also asked the experts to assess duration, breaking each case into three time periods: the acute, rehabilitation, and long-term phases. We requested that they assess each injury separately and assess the combined effects of all injuries for each of the multiple injury cases.
For the other two indexes, we used values from previously completed research. For the QWB, we relied on data provided by Troy Holbrook of the University of California, San Diego. Holbrook’s team used patient self-assessments to determine the attributes associated with various injuries, for individuals age 18 or older (Holbrook et al., 1999).19 The resulting HRQL estimates are available by body region and injury severity (based on the six major AIS categories) for four time periods: predischarge, and at 6, 12, and 18 months. We matched these data with the body regions and AIS scores for each injury in our data set, focusing on the injury identified as the MAIS in multiple injury cases. We applied the Holbrook predischarge values to the hospitalization period, then applied the 6-month values from discharge (or injury date, if not hospitalized) to 6 months, the 12-month values from 6 to 12 months, and the 18-month values from 12 months through the remaining lifespan.
The fourth index used was the FCI, which is currently being developed (with NHTSA support) to measure the impacts of nonfatal injuries on functional status. It differs from the other indexes in that it is not intended to reflect all aspects of HRQL. Furthermore, it is not yet widely validated or
Holbrook also provided adolescent data, but we used the adult values because of the small size of the adolescent sample. Comparison of the adolescent and adult values showed a lower “with injury” HRQL for adults, as expected, given that adolescents are likely to be in better health, on average, absent injury.