Laboratory Diagnosis of DIC: The Consumptive Coagulopathy Pattern
Key Point
DIC is characterized by simultaneous consumption of clotting factors and platelets coupled with secondary fibrinolysis. The combination of low fibrinogen, elevated FDP, and prolonged PT/aPTT is pathognomonic.
The DIC Laboratory Triad
| Finding | Mechanism | Why It Occurs |
|---|
| Low fibrinogen | Consumption by thrombin | Widespread fibrin formation depletes fibrinogen |
| Elevated FDP | Secondary fibrinolysis | Plasmin degrades deposited fibrin |
| Prolonged PT/aPTT | Factor consumption | Factors II, V, VII, VIII, X, XIII consumed |
| Thrombocytopenia | Platelet consumption | Incorporated into microthrombi |
| Elevated D-dimer | Fibrin breakdown | Highly sensitive but NOT specific |
High-YieldNEET PG
The combination of low fibrinogen + elevated FDP + prolonged PT/aPTT + thrombocytopenia = DIC. No single test is diagnostic; you need the pattern.
Why Each Finding Matters
- 1.
Fibrinogen — decreases progressively as it is consumed
- 2.
FDP (fibrin degradation products) — rises due to secondary fibrinolysis (plasmin degrades fibrin clots)
- 3.
PT/aPTT — prolonged because clotting factors are consumed
- 4.
Platelets — fall due to incorporation into microthrombi
Clinical Pearl
In chronic DIC (e.g., malignancy), fibrinogen may be normal or elevated because the liver compensates with increased synthesis. In acute DIC (sepsis, trauma), fibrinogen drops rapidly.
DIC Scoring System (ISTH)
DIC diagnosis requires:
A score ≥ 5 is compatible with overt DIC.
