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ISTH Overt DIC Score

The ISTH overt DIC score (0–8) combines platelet count, fibrin-related marker (D-dimer/FDP), PT prolongation and fibrinogen in a patient with an underlying disorder known to cause DIC. A score ≥5 is compatible with overt DIC; <5 is suggestive of non-overt DIC, repeat in 1–2 days.

Platelet count (×10⁹/L or ×10³/µL)
Fibrin-related marker (D-dimer / FDP): No increase (0); Moderate increase (2); Strong increase (3)
PT prolongation above upper limit of normal (s)
Fibrinogen (mg/dL or g/L)

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Interpretation

Result	Meaning
≥ 5	Compatible with overt DIC
< 5	Suggestive (not affirmative) of non-overt DIC; repeat in 1–2 days

Formula

Platelets ≥100 = 0, 50–99 = 1, <50 = 2 · fibrin marker none 0, moderate 2, strong 3 · PT prolongation <3 s = 0, 3–6 s = 1, >6 s = 2 · fibrinogen ≥1 g/L = 0, <1 g/L = 1

Clinical pearls

Only apply in a patient with an underlying disorder associated with DIC (sepsis, trauma, malignancy, obstetric catastrophe).
"Moderate" vs "strong" D-dimer increase is assay-specific; many labs define strong as >10× the upper limit of normal.
Trends (falling platelets, rising PT) matter more than one score.

Examples

isth dic plt 40 d-dimer strongly elevated pt prolonged 4 s fibrinogen 80 mg/dL dic score platelets 120, moderate ddimer, pt 2 sec over, fib 2.0 g/L does a septic patient with platelets 60 and fibrinogen 0.9 g/L have dic

FAQ

What ISTH score means DIC?

A total of 5 or more is compatible with overt DIC.

What counts as a moderate or strong D-dimer increase?

The ISTH left this assay-dependent; commonly moderate is above the upper limit of normal and strong is above 10 times the upper limit.

Evidence

Taylor FB Jr et al. Towards definition, clinical and laboratory criteria, and a scoring system for disseminated intravascular coagulation. Thromb Haemost 2001;86:1327–30.

Hematology & Oncology · Reviewed 2026-10-14 · Methodology