Skip to main content


As part of our Journal Club summaries our JC Chairs (Drs. Lisa Calder and Ian Stiell @EMO_Daddy) have been tasked with explaining Epidemiological concepts so that everyone in our department can analyze the literature and appraise articles on their own. For this Blog post we have all the "Epi Lessons" as they relate to "Decision Rules Articles". More to follow in the coming weeks.

Approach to Decision Rule Development                                                                 
By: Dr. Venkatesh Thiruganasambandamoorthy
In this era of clinical decision tools being developed for almost anything, we need to think will a clinical decision tool be helpful and how to use them. There are methodological standards that have been developed (i.e. when should one try to develop a tool, how to do it and the stages towards developing a robust tool).
i)               There must be a need due to prevalence of the clinical condition and current practice. Such a need must be a belief among physicians practicing in that area
ii)              The outcome or diagnosis to be predicted must be clearly defined. Assessment of the outcome should be made without knowledge of the predictor variables (Blinded outcome assessment);
iii)            The clinical findings to be used as predictors must be clearly defined, standardized, and clinically sensible and their assessment must be done without the knowledge of the outcome (Blinding for the outcome, blinded variable collection);
iv)            The reliability or reproducibility of the predictor findings must be clearly demonstrated (usually reported as kappa for the predictors);
v)             To increase generalizability, the subjects in the study should be selected without bias and should represent a wide spectrum of patients with and without the outcome;
vi)            Sound mathematical techniques must be used for deriving the tools and must be clearly explained;
vii)          Decision tools should be clinically sensible and their accuracy must be demonstrated:
viii)         Prospective validation is an essential step in the evolution of this form of decision support. Implementation phase (to demonstrate the true effect on patient care) is the ultimate test of a decision tool.

Not all clinical decision tools are developed for simple decisions (x-ray or not), some are developed to aid complex decision making process. As physicians, we must use our clinical acumen to incorporate these tools in our practice (e.g. using the risk factors identified among syncope patients to ensure that no serious conditions already exist, among patients with multiple comorbidities using these tools to make shared decisions with patients/families or identification of patients for further outpatient consultations/testing).

Methodological Standards for Clinical Decision Rules      
                                                                              By: Dr. Lisa Calder             January 2013
As more clinical decision rules are created, this will lead to further systematic literature reviews of such rules. This raises the challenge of evaluating methodological quality of clinical decision rules. There are standards published in the literature for emergency medicine – these include: well defined and prospectively collected predictor variables, well defined clinically important outcomes and prospective validation. 

Stages of Clinical Decision Rule Development
                                             By: Dr. Lisa Calder & Ian Stiell        October-November 2014 Clinical Decision Rules require 4 key stages of development prior to adoption in to clinical practice: derivation, prospective validation, evaluation of implementation and knowledge translation. The first step entails a derivation study that ideally is conducted prospectively and has a large number of outcome cases. The second step is a prospective validation study that explicitly evaluates the new rule for accuracy, physician acceptability and potential impact. The third step is an implementation trial to evaluate the actual impact of the rule on patient outcomes in real clinical practice.  Be very cautious incorporating any decision rule into your practice which has not been through at least the first two steps.  Examples of such rigorous decision rules include the Canadian CT head rule, Canadian C-spine rule and Ottawa Ankle rule. 

Validation of clinical decision rules                 By: Dr. Ian Stiell               November 2012 

Critical appraisal criteria for a paper that validates an existing decision rule are different than those for a study that derives or creates the rule. Most important is that the study evaluates the existing rule accurately and explicitly such that the physicians using it are adequately instructed. Some studies do a validation from an existing database but we believe that it is far better to conduct a prospective real-time validation by clinicians. 

What is a Clinically Sensible Clinical Decision Rule?          
                                                               By: Dr. Ian Stiell                                    March 2015
Clinical decision rules for emergency medicine should be “clinically sensible.” This means the rules should be easy to use and comprised of as few variables as possible. Emergency physicians prefer rules that give a simple yes/no answer or use a basic scoring system that can be quickly calculated. The component variables should make have good face validity for clinicians

What is Collinearity? Why does it Matter? How do you Measure it?
By: Dr. Christian Vaillancourt
Collinearity means that two of the predictors entered in a regression analysis model correlate with each other (they measure almost the same thing, e.g. %body fat and total body weight). When more than two predictors interact with each other, it is called multicollinearity.Collinearity can be a problem, especially when very high, since the software will simply not be able to perform the regression analyses, or will provide unreliable results. The degree of collinearity can be estimated using the Variance Inflation Factor (VIF) which should be <5-10.


Popular posts from this blog

Tips for Success in your Emergency Medicine Rotation

Our wonderful medical students are preparing to start their first clinical rotations. With this in mind here are some of the top tips for success in your EM rotation
1)Be On Time – show up to your shifts on time, better yet 5 minutes early.That first impression is immensely important.
2)Introduce yourself to the team - “Hi my name is John Doe, I am the medical student on shift today” introduce yourself to the attending, residents, nurses, etc.You will be called on a lot more to help when there is something interesting going on if they know your name.
3)Be goal-oriented – have a goal for each shift, whether it’s a procedure or a type of presentation to see.
4)Don’t just stand there, do something – whenever there is a trauma or code, come to the bedside.Get gowned up for traumas and pay attention.Help with things that are within your scope of practice: chest compressions, moving patient, cardioversion
5)Don’t just stand there, do nothing – there are times in medicine when the best thing to d…

2014 Canadian Guidelines for AF Management: Part 1: Introduction and CCS “CHADS-65” Algorithm

by Ian Stiell MD @EMO_Daddy

In this and subsequent postings we will discuss the latest recommendations for ED management of atrial fibrillation (AF) as presented in the newly published 2014 Focused Update of the Canadian Cardiovascular Society Guidelines for the Management of Atrial Fibrillation. The Guidelines PDF can be downloaded from the CCS website at 2014 Canadian Cardiovascular Society Guidelines for the Management of Atrial Fibrillation
The 2014 Focused Update uses the GRADE system of evidence evaluation as was the case in the comprehensive 2010 AF Guidelines and the 2012 Update. The CCS AF Guidelines Panel is comprised of Canadian cardiologists plus physicians from internal medicine, family medicine, neurology, and emergency medicine. This 2014 Update provides evidence review and recommendations for 8 aspects of AF care, including ED Management (written by myself and Dr. Laurent Macle of the Montreal Heart Institute). The 2014 Update focuses on advances in oral anticoagulant (O…

You CAN reverse that! Reversal of NOAC's and more..

We have seen a large surge of the utilization of New Oral Anticoagulants (NOAC's) in the past few years, as such, it has been a novel challenge when these patients present to the Emergency Department (ED) with life threatening bleeding. Dr. Michael Ho looks to discuss treatment options, and future options in these patients. 
NOACs vs WarfarinDabigatran, Rivaroxaban and Apixaban have seen a dramatic increase in use since their approval in Canada. Dabigatran is a direct thrombin (Factor II) inhibitor, while the latter two are direct Xa inhibitors. These drugs are collectively referred to as novel oral anticoagulants (NOACs). They have also been called direct, or target-specific oral anticoagulants (DOACs or TSOACs) [1]. 
The NOACs have many practical advantages over warfarin: Rapid onset of actionShorter half-lifeLess food and drug interferencePredictable pharmacokineticsEase of use and no requirement for monitoringThe downsides to NOACs are the higher cost to the patient, the inabilit…