ISTH DIC Score
The ISTH scoring system for overt disseminated intravascular coagulation uses platelet count, fibrin markers (D-dimer/FDPs), prothrombin time prolongation, and fibrinogen level. A score ≥5 is compatible with overt DIC.
inputs
✓ when to use
Use in patients with a clinical condition known to be associated with DIC (sepsis, trauma, obstetric complications, malignancy, acute promyelocytic leukaemia) who have laboratory evidence of coagulopathy. The ISTH scoring system should only be applied when an underlying diagnosis associated with DIC is present.
✗ when not to use
Do not apply the scoring system without an underlying predisposing condition — isolated lab abnormalities can have many causes. The score reflects overt DIC; non-overt (compensated) DIC exists below the ≥5 threshold. The 'fibrin marker' criterion is relative to local lab ranges and requires clinical interpretation. Not a standalone diagnostic test.
clinical pearls
- The ISTH score requires a known underlying cause of DIC — do not apply it as a screening tool in patients without a predisposing condition. The most common causes are sepsis, trauma, obstetric emergencies, and malignancy.
- Treat the cause, not the score. DIC is always secondary to an underlying condition. The single most important intervention is treating that underlying cause (antibiotics for sepsis, delivery for obstetric DIC, chemotherapy for APML).
- Fibrinogen is an acute-phase reactant — it can be 'normal' in DIC if the patient has a concurrent inflammatory state elevating it. A fibrinogen that is falling (even if still >1.0 g/L) may be more significant than a single low value.
- Serial scoring (daily or more frequently in ICU) is essential. DIC is a dynamic process — a score of 3 today may be 6 tomorrow. Trending is more informative than single values.
- The D-dimer/FDP criterion uses relative thresholds ('moderate' vs 'strong' increase), not absolute values. This requires familiarity with your lab's reference ranges and assay. What constitutes a 'strong increase' differs by assay.