Which statement about D-dimer testing is true?

• A. D-dimer is insensitive to fibrinolysis
• B. D-dimer is a specific product of cross-linked fibrin degradation
• C. D-dimer does not reflect thrombosis
• D. D-dimer is produced by platelets

Answer: (B)

D-dimer testing detects a fragment released when a fibrin clot is broken down by plasmin. Fibrin that has been stabilized by factor XIII’s cross-linking, once degraded, yields a specific fragment known as D-dimer. This makes D-dimer a distinctive product of cross-linked fibrin degradation and a marker of thrombus formation with active fibrinolysis. It is not produced by platelets, and while a positive result indicates recent clot breakdown, it isn’t perfectly specific to thrombosis because other conditions with fibrin turnover can raise D-dimer levels. The statement that D-dimer is a specific product of cross-linked fibrin degradation is the true one.