An evaluation of multiple trauma severity indices created by different index development strategies.

Evaluation of the effectiveness of emergency trauma care systems is complicated by the need to adjust for the widely variable case mix found in trauma patient populations. Several strategies have been advanced to construct the severity indices that can control for these population differences. This article describes a validity and reliability comparison of trauma severity indices developed under three different approaches: 1) use of a multi-attribute utility (MAU) model; 2) an actuarial approach relying on empirical data bases; and 3) an "ad hoc" approach. Seven criteria were identified to serve as standards of comparison for four different indices. The study's findings indicate that the index developed using the MAU theory approach associates most closely with physician judgments of trauma severity. When correlated with a morbidity outcome measure, the MAU-based index shows higher levels of agreement than the other indices. The index development approach based on the principles of MAU theory has several advantages and it appears to be a powerful tool in the creation of effective severity indices.