Table 4.

Differences Between BLS and ALS in 90-d Survival, by Trauma Subgroups^*

Subgroup	BLS, n	ALS, n	Survival Difference in Propensity Score Analysis (95% CI), percentage points	Survival Difference in Instrumental Variable Analysis (95% CI), percentage points
Low severity†	27 297	39 341	4.6 (4.0 to 5.3)	2.7 (−0.2 to 5.5)
High severity‡	3622	9427	14.7 (12.7 to 16.7)	12.5 (4.7 to 20.2)
Accidental falls	7568	11 947	4.8 (3.5 to 6.2)	7.1 (2.0 to 12.3)

ALS = advanced life support; BLS = basic life support.

^*Propensity score estimates are the difference in 90-d survival between BLS and ALS recipients, adjusted by propensity score–based balancing weights. The instrumental variable estimates represent the effect on survival of receiving BLS rather than ALS for a “switcher” (i.e., a person who would receive BLS in an area with a higher rate of BLS use but ALS in an area with lower BLS use). Accidental falls were analyzed only for 2010 and 2011, in which separate external-cause code fields existed and were complete for 92% of observations.

^†New Injury Severity Score between 16 and 24.

^‡New Injury Severity Score between 25 and 75.