Methodological Challenges in Studies Comparing Prehospital Advanced Life Support to Basic Life Support

Background/Purpose

Acute emergencies are among the leading causes of death. Therefore, determining the most appropriate level of emergency medical services (EMS) care for patients in the prehospital setting is essential. A large body of literature suggests that, compared to basic life support (BLS), advanced life support (ALS) does not lead to decreased mortality. The purpose of this review was to synthesize the literature to identify common study design and analytic challenges in studies that examine the effect of ALS, compared to BLS, on patient outcomes. 

Methods

The literature was reviewed to identify studies comparing ALS care to BLS care. Articles in the 2011 meta-analysis by Bakalos et al. were selected for review as this is the most recent meta-analysis on this topic. Other studies were also identified through a MEDLINE search and a review of the reference lists of articles included in the meta-analysis by Bakalos et al.

Results

Several themes related to challenges associated with studies that compared ALS to BLS care were identified, including: 1) choice of outcome measure, 2) logistic regression modeling of common outcomes, 3) baseline differences between study groups (confounding), 4) inappropriate statistical adjustment, and 5) inclusion of patients who are no longer at risk for the outcome. 

Conclusions

These challenges may affect the results of studies and thus, conclusions of studies regarding the effect of level of prehospital care and patient outcomes may require cautious interpretation. Specific alternatives for avoiding these challenges are presented.