Clinical prediction rules are decision-making tools that incorporate three or more variables from the history, physical examination or simple tests. They help clinicians make diagnostic or therapeutic decisions by standardizing the collection and interpretation of clinical data. There is growing interest in the methodological standards for their development and validation. This article describes the methods used to derive the Canadian C-Spine Rule and provides a valuable reference for investigators planning to develop future clinical prediction rules.

This paper is Part I of a 2-part series to describe the background and methodology for the Canadian C-Spine Rule study to develop a clinical decision rule for rational imaging in alert and stable trauma patients. Current use of radiography is inefficient and variable, in part because there has been a lack of evidence-based guidelines to assist emergency physicians. Clinical decision rules are research-based decision-making tools that incorporate 3 or more variables from the history, physical examination or simple tests. The Canadian CT Head and C-Spine (CCC) Study is a large collaborative effort to develop clinical decision rules for the use of CT head in minor head injury and for the use of cervical spine radiography in alert and stable trauma victims. Part I details the background and rationale for the development of the Canadian C-Spine Rule. Part II will describe in detail the objectives and methods of the Canadian C-Spine Rule study.