The Resus Room One for the geeks; interval likelihood ratios
Risk assessment, testing and risk management form the very heart of Emergency Medicine and Critical Care.
Being aware of the evidence surrounding a topic is key to delivering high level care but without an understanding of the underpinning concepts it's application is extremely limited.
Understanding how a test result changes a patient's likelihood of a disease can be described with likelihood ratios, the Royal College of Emergency Medicine has a podcast explaining likelihood ratios in more detail.
But when a test result comes back on the boundary between positive and negative, or at the extremes of positive we can find it difficult to know what this means and that's where interval likelihood ratios comes into play.
Examples include a minimally elevated WCC in a suspected appendicitis, or a dramatically raised d-dimer as compared to a borderline positive result in a suspected pulmonary embolus, this podcast talks through some of those concepts and their application, enjoy!
References
Pulmonary embolism: making sense of the diagnostic evaluation. Wolfe TR. Ann Emerg Med. 2001