The latest CAN is one of our brand-new 'revision editions' -- brief podcasts aimed at covering the essentials of critical appraisal for medical students and junior doctors preparing for exams.
With the help of Gregory Yates, an academic doctor based in Manchester, this episode introduces two core concepts: sensitivity and specificity. These are two ways of thinking about the accuracy of a diagnostic test. Knowing the sensitivity and specificity of an investigation will give you a decent idea of how it should be used in the emergency department.
Sensitivity (Sn) describes the chance that a test will be positive if your patient has the condition you're testing for. Some people call it the 'true positive rate' or alternatively the positivity in disease (PID) rate. If you need a hand remembering it, you can always remember that PID is a sensitive issue.
Meanwhile, specificity (Sp) considers the chance of a test being negative if the patient doesn't have the condition you're testing for. It's the 'true negative rate' or alternatively the negativity in health (NIH) rate. There are times when we particularly need a test to have a high sensitivity. This is generally when we want to be particularly confident that a test accurately identifies everyone with the relevant condition because we really don't want to miss it. We need a high sensitivity to rule out disease. (Sn-uff it out). At other times, we need to be confident that a patient with a positive test actually has the disease - for example, if the treatment is unpleasant or involves exposing patients to risk. In that case, we want a high specificity to rule in disease. (Sp-in it in).
In this CAN, we use D-Dimer as an example of a very sensitive investigation: it’s positive in nearly 100% of cases of venous thromboembolism. Specificity describes the likelihood that the test will be negative if your patient does not have the disease. We use HbA1c as an example of a highly specific investigation: it’s rarely used in the emergency department, but if it’s elevated, we can be almost certain that the patient is diabetic. HbA1c is almost never (
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Ep 150 - REBOA with Zaf Qasim
Ep 149 - September 2019 Round Up
Ep 148 - CRASH-3
Ep 147 - August 2019 Round Up
Ep 146 - European Resus Council meeting Slovenia 2019
Ep 145 - The UK Resuscitationist with Dan Horner at #stemlynsLIVE
Ep 144 - July 2019 Round Up
Ep 143 - The Future of Diagnostics with Rick Body
Ep 142 - Psychological performance in the Resus Room with Ashley Liebig
Ep 141 - June 2019 Round Up
Ep 140 - GI emergencies with Chris Gray at #stemlynsLIVE
Ep 139 - May 2019 Round Up
Ep 138 - Traumatic Cardiac Arrest with Prof Jason Smith RN
Ep 137 - Beyond ATLS with Alan Grayson at #stemlynsLIVE
Ep 136 - Wellbeing for the broken with Liz Crowe
Ep 135 - April 2019 Round Up
Ep 134 - March 2019 Round Up
Ep 133 - February 2019 Round Up
Ep 132 - Aortic Emergencies with George Wills at #stemlynsLIVE
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