You are not logged in. Only partial content from the Question of the Day will be available to you. To view the full content of this Question of the Day, you must log in to your account. Don't have a login? Register now. Or, check out our Preview.
Week 5: Diagnostic Testing
Today, we continue our discussion of diagnostic testing and discuss changes in probability of disease. We will start off with the same example as yesterday.
A 55-year-old man with a history of heart failure and COPD is evaluated for SOB and tachycardia after a cross-country road trip. On exam, he has bibasilar crackles and CXR shows mild pulmonary edema. He denies hemoptysis, malignancy, prior venous thromboembolism, or lower extremity complaints. Does the patient have a PE?
The d-dimer is a marker for clot activity. It has a high sensitivity, ranging from 70-100%, and is useful in ruling out disease. The d-dimer of <500 ng/mL decreases the probability from 6-10% pretest to 1-2% posttest. The posttest probability is not zero but it is generally considered low enough to rule out PE.