Centre for Evidence-Based Medicine
Pretest Probability is defined as the probability of a patient having the target disorder before a diagnostic test result is known.
The Likelihood Ratio (LR) is the likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that that same result would be expected in a patient without the target disorder.
This exercise is designed to walk you through the process of going from your “PICO” question to the steps of a rapid search for the evidence.
This document explains the background to the Oxford Centre for Evidence Based Medicine’s Levels of Evidence.
This must be read before using the Levels: no evidence ranking system or decision tool can be used without a healthy dose of judgment and thought.
This is the first version of the Levels of Evidence, last revised in March 2009