Post by William Love

One of the easiest mistakes in medicine is also one of the most understandable. We fail to find something. Then, almost without noticing, we begin reasoning as though it isn’t there. A normal mammogram does not prove the absence of breast cancer. A normal ECG does not prove the absence of arrhythmia. A normal stress test does not prove the absence of all cardiac disease. Physicians understand this. That’s why we think in terms of sensitivity, specificity, pretest probability, and diagnostic uncertainty. But something interesting happens when symptoms persist. The longer an evaluation remains unrevealing, the easier it becomes to conclude that the absence of evidence is evidence of absence. Sometimes that’s correct. Often it isn’t. The history of medicine is full of examples where reality existed before we had the tools, concepts, or conditions necessary to detect it. The challenge is not believing everything. The challenge is avoiding the opposite error: Mistaking the limits of our evaluation for the limits of reality. Good clinical reasoning requires holding two ideas simultaneously: A finding has not been demonstrated. Therefore it should not be assumed. A finding has not been demonstrated. Therefore it should not be excluded. Those are not contradictory statements. They are the foundation of diagnostic humility. What is the best example in your field of something that existed long before medicine could reliably detect it? #ClinicalReasoning #Diagnostics #MedicalEducation #InternalMedicine #PatientCare