Outcomes of Basic Versus Advanced Life Support for Out-of-Hospital Medical Emergencies

Stephen B. Soumerai

doi:10.7326/L15-0627

Letters |5 July 2016

Outcomes of Basic Versus Advanced Life Support for Out-of-Hospital Medical Emergencies

Stephen B. Soumerai, ScD

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TO THE EDITOR:

The recent article by Sanghavi and colleagues reports interesting Medicare claims data on the reduced survival of patients receiving advanced life support (ALS) versus basic life support (BLS) ambulances (1). Unsurprisingly, as with all research, this study raises important questions about bias and confounding.

First, the authors used a cross-sectional design with no estimate of pre–post change and no adequate counterfactual (control). Although conducting a randomized, control trial (RCT) is difficult, a hierarchy of quasi-experimental (non-RCT) designs produce differing levels of validity of causal inferences (2). The cross-sectional design, with or without propensity score adjustments or instrumental variables (IVs), is not included as evidence in international systematic reviews (3). Although natural experiments of changing ambulance services are hard to find, this weak design casts doubt on the authors' near-causal inferences that “we found similar or better health outcomes associated with prehospital BLS than ALS.”

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2016 American College of Physicians

Letters |5 July 2016

Outcomes of Basic Versus Advanced Life Support for Out-of-Hospital Medical Emergencies

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Letters |5 July 2016

Outcomes of Basic Versus Advanced Life Support for Out-of-Hospital Medical Emergencies

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