In disseminated intravascular coagulation (DIC), which laboratory finding indicates depletion of clotting factors?

• A. Platelets 100,000/mm3
• B. Fibrinogen levels 57 mg/dL
• C. Fibrin degradation products 4.3 mcg/mL
• D. D‑dimer 0.03 mcg/mL

Answer: (B)

In DIC, coagulation is activated throughout the circulation, consuming clotting factors and platelets in the process. When fibrinogen, a key clotting factor, is consumed faster than it’s produced, its level falls. A fibrinogen level as low as 57 mg/dL shows that clotting factors are depleted, which greatly increases bleeding risk because there isn’t enough fibrinogen available to form stable clots. Normal fibrinogen is roughly 200–400 mg/dL, so this profound drop points to depletion of clotting factors. Other changes in DIC reflect different aspects: platelets can be low from consumption, while fibrin degradation products and D-dimer rise from increased breakdown of clots. So the profoundly low fibrinogen level is the clearest sign of depletion of clotting factors in DIC.