Sensitivity and Specificity as Guides to Clinical Decision Making

From headache to helping hand Many of us get headaches and go cross-eyed when we see statistical concepts like sensitivity and specificity in print. Usually, these appear in articles about a diagnostic test's ability to tell you when a condition or disease state is present (i.e., sensitivity) or, conversely, to tell you when that condition or disease state isn't there (i.e., specificity). An initial 12-lead ECG, for example, has a sensitivity of about 68% for diagnosing an acute ST-elevation myocardial infarction (STEMI). That means that a little more than two-thirds of patients who eventually rule-in for MIs are going to have ST elevations on their initial ECGs. What this translates to on the street is that a nondiagnostic ECG (no ST elevations) probably shouldn't be used to withhold aspirin in a suspected MI, or to support a patient's decision to refuse transport; otherwise, there's a reasonable chance that you and your patient are going to get into trouble about one-third of the time (32%). On the flip side, an ECG's ability to detect a STEMI has a specificity of about 97%. In other words, if the patient isn't having a STEMI, then there's only a very small chance that they're going to have ST elevations that look like they're having one (3%). What this all means is that a 12-lead ECG is a good way to rule-in an MI when ST-elevations are present (68%), but it's a bad way to rule one out when those changes aren't (32%). There's also a small chance that y...
Source: JEMS Patient Care - Category: Emergency Medicine Authors: Tags: Patient Care Columns Source Type: news