Table 5.

Survival benefit of HEMS measured by TRISS and RISC

	HEMS	GEMS	P-value
TRISS
Number of cases	2,949	4,467
Expected mortality	20.4%	17.5%	-
Observed mortality	13.8%	14.4%
Standardized Mortality Ratio (95% CI)	0.678 (0.617 to 0.739)	0.825 (0.766 to 0.884)	0.0011
RISC
Number of cases	4,575	7,469
Expected mortality	18.3%	17.2%	-
Observed mortality	14.6%	14.9%
Standardized Mortality Ratio (95% CI)	0.798 (0.742 to 0.854)	0.869 (0.822 to 0.916)	0.062