These scores are produced by a method of direct standardization of the difference between the observed number of survivors and the TRISS-predicted number of survivors according to the case mix of injury severity of the US prediction database.
After standardization according to the case mix of injury severity of the US prediction database, the Ws and Zs scores were, respectively, 3.3 (95% CI 1.9 to 4.6) and 4.81 (P < 0.0001) among whole-body CT patients, indicating a significantly better survival in these patients than that predicted by the TRISS method.
Although much of the Rim fire burned during plume-dominated conditions resulting in large high-severity patches, our study area burned under milder fire weather resulting in a mix of fire severities.
Practice pattern variation has been attributed to many factors, including patient case mix and severity of illness, availability of resources and characteristics of the individual physician themselves [ 3, 4].
For performing the TRISS analysis, we found an acceptable distribution of severity mix in the before and after group (M = 0.94 vs. M = 0.93).
The intensity of the fires varied across the landscape, with a mix of low to moderate severity, and lesser amounts of high burn severity.
Fifth, our study was single center, which also limits its external validity; however, our critical care unit is comparable to most multidisciplinary university-affiliated North American PICUs with regard to case mix and severity of illness.
There is great international variability in patient mix and severity of illness [ 7, 8, 9, 16, 17, 18].
When the eligible patient population can be defined appropriately, process measures are typically insensitive to differences in case mix and severity of illness [ 1, 26- 28].
