Choice and discussion of laboratory parameters in DIC syndrome.
- DIC is a pathological process characterized by the widespread activation of the clotting cascade
- results in the formation of blood clots in the small blood vessels throughout the body
- = compromise of tissue blood flow and can ultimately lead to multiple organ damage
- **the coagulation process consumes clotting factors and platelets, normal clotting is disrupted and severe bleeding can occur from various sites**
- Causes for DIC
- Massive tissue injury: severe trauma, burns, hyperthermia, rhabdomyolysis, extensive surgery
- Severe allergic or toxic reactions (i.e. snake or viper venom)
- Giant hemangiomas (Kasabach-Merritt syndrome)
- Large aortic aneurysms
- Acute form– secondary fibrinolysis has a leading role and bleeding is the main symptom
- Chronic form – the clotting cascade is activated and there are symptoms of thrombosis. This form is typical for malignant diseases.
Investigation
If disseminated intravascular coagulation (DIC) is suspected then clotting screen tests are followed by confirmation:
- Prothrombin time (PT) elevated
- Activated partial thromboplastin time (aPTT) elevated
- Platelet count reduced
- Fibrinogen level low
If two results are positive, diagnosis is possible; if three are positive, it is likely; if all four are positive, it is extremely likely.
Confirmatory tests look for evidence of the simultaneous formation of thrombin and plasmin.
- The D-dimer test gives strong evidence of DIC
- Fibrin degradation products (FDPs) are helpful but can occur in other conditions such as deep vein thrombosis (DVT) and, in severe disease, they may be negative
- In acute DIC, PT and aPTT are prolonged, and the platelet count and fibrinogen decrease. D-dimer, FDP, and fibrin monomer levels are elevated
In subacute or chronic DIC, PT and aPTT may be prolonged or normal. The fibrinogen level is decreased modestly and, in some cases, may be within the reference range or increased. Platelets may be slightly low or normal. D-dimer and FDP are slightly elevated.
DIC is progressing in 3 phases and lab results are different during each of these phases.
- There is NO specific laboratory test for DIC. Other tests may be useful but do not confirm the diagnosis.
- Thrombin time can be prolonged because of fibrinogen consumption
- Thrombin-antithrombin complexes in plasma suggests prior thrombin formation
- Antithrombin levels seem more promising than fibrinogen levels
A scoring system has been developed to aid diagnosis and it correlates with 28 days' mortality.It is based on the wave form of aPTT. Such a system may also help assess the response to treatment.