Article Text

Download PDFPDF
Assessing patient safety risk before the injury occurs: an introduction to sociotechnical probabilistic risk modelling in health care
  1. D A Marx1,
  2. A D Slonim2
  1. 1President, Outcome Engineering LLC, Dallas, TX, USA
  2. 2Children’s National Medical Center, The George Washington University School of Medicine, Washington, DC, USA
  1. Correspondence to:
 Mr D A Marx
 President, Outcome Engineering LLC, Dallas, TX, USA; dmarx{at}


Since 1 July 2001 the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has required each accredited hospital to conduct at least one proactive risk assessment annually. Failure modes and effects analysis (FMEA) was recommended as one tool for conducting this task. This paper examines the limitations of FMEA and introduces a second tool used by the aviation and nuclear industries to examine low frequency, high impact events in complex systems. The adapted tool, known as sociotechnical probabilistic risk assessment (ST-PRA), provides an alternative for proactively identifying, prioritizing, and mitigating patient safety risk. The uniqueness of ST-PRA is its ability to model combinations of equipment failures, human error, at risk behavioral norms, and recovery opportunities through the use of fault trees. While ST-PRA is a complex, high end risk modelling tool, it provides an opportunity to visualize system risk in a manner that is not possible through FMEA.

  • patient safety
  • sociotechnical probabilistic risk assessment (ST-PRA)
  • root cause analysis
  • quality improvement
  • risk management

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Outcome Engineering is a Dallas, Texas based risk management firm building risk management methodologies for the aerospace and healthcare industries. Mr Marx is a principal in Outcome Engineering LLC.