D-Dimer is a specific indicator of what process, and is elevated in which conditions?

• A. Indicator of liver enzyme activity
• B. Marker for hydration status
• C. Specific indicator of fibrinolysis, the natural process that breaks down clots. Elevated in thrombotic disorders such as DVT and PE
• D. Indicator of coagulation factor production

Answer: (C)

D-dimer reflects fibrinolysis, the body's process of breaking down a clot. When a clot forms, cross-linked fibrin is laid down and later dissolved by plasmin, producing D-dimer fragments that can be measured in the blood. A detectable D-dimer means that clot breakdown is occurring, which happens in conditions with clot formation and turnover. It is elevated in thrombotic disorders such as deep vein thrombosis and pulmonary embolism, and can also rise in other states with increased fibrin formation and breakdown (for example after surgery, trauma, infection, cancer, or disseminated intravascular coagulation). It is not a measure of liver enzyme activity, hydration status, or coagulation factor production. Clinically, a negative D-dimer can help rule out thrombosis in patients with low suspected probability, whereas a positive result requires imaging confirmation due to limited specificity.