A Tragedy within a Tragedy: How the Inappropriate Request for D-dimer during the COVID-19 Pandemic Might Have Harmed So Many People

The COVID-19 pandemic was a global tragedy, resulting in the deaths of millions of individuals. It also exposed serious flaws in medical education, particularly regarding the proper interpretation of scientific evidence and diagnostic tests. In this regard, the unnecessary ordering and misinterpretation of D-dimer stands out, as it has exposed many patients to the risks of unnecessary anticoagulation and may have led to iatrogenic outcomes. In this article, we review the characteristics of D-dimer as a diagnostic test, integrating with the understanding of physiological and pathological hemostasis and through a mathematical simulation, demonstrate how a considerable number of people might have been harmed by the misinterpretation of the test and yet, paradoxically, it could still appear that anticoagulation was the appropriate course of action, due to cognitive biases that can make an incorrect approach seem correct when interpreted retrospectively. Authors' Contributions Y.G.: Conceptualization, writing–original draft, writing–reviewing and editing. J.N.A.: Writing–original draft, writing–reviewing and editing. Publication History Received: 15 August 2025 Accepted: 08 December 2025 Article published online: 22 December 2025 © 2025. Thieme. All rights reserved. Thieme Medical Publishers, Inc. 333 Seventh Avenue, 18th Floor, New York, NY 10001, USA