D-dimer - a multifaceted molecule

D-dimer, a universally unique marker for fibrin degradation, is generated through the enzymatic interplay of thrombin, factor XIIIa, and plasmin. The emergence of D-dimer-containing fibrin molecules occurs in both intravascular and extravascular spaces during pivotal physiological processes like haemostasis, thrombosis, and tissue repair. Given the inherently physiological nature of fibrin formation and fibrinolysis, basal levels of D-dimer fragments are present in plasma. Beyond its role as a marker of routine physiological processes, aberrations in D-dimer levels are indicative of a spectrum of conditions, both non-pathological and pathological. The clinical utility of D-dimer has been firmly established, particularly in scenarios like venous thromboembolism (VTE), pulmonary embolism (PE), deep vein thrombosis (DVT), and disseminated intravascular coagulation (DIC). Additionally, recent applications have extended to assess the prognosis of COVID-19. While D-dimer is commonly associated with thrombotic conditions, its elevation is not confined to these conditions alone. Elevated D-dimer levels are observed across various diseases, where its significance extends beyond diagnostic indicators to prognostic implications.