DIC Syndrome Calculator — ISTH Overt DIC Score
The ISTH (International Society on Thrombosis and Haemostasis) DIC scoring system quantifies the likelihood of overt disseminated intravascular coagulation from four routine coagulation tests. A score ≥ 5 is compatible with overt DIC.
Platelet count (×10⁹/L)
D-dimer / fibrin degradation products
Prothrombin time (PT) prolongation above ULN
Fibrinogen level
Score < 5 — not overt DIC. Repeat in 1–2 days if DIC is clinically suspected.
- 1
Platelet score
0 - 2
D-dimer / FDP score
0 - 3
PT prolongation score
0 - 4
Fibrinogen score
0 - 5
ISTH DIC score
0 + 0 + 0 + 0 = 0
How does this calculator work?
The ISTH overt DIC score sums four ordinal scores: platelets (0–2), D-dimer/FDP (0–3), PT prolongation (0–2), and fibrinogen (0–1), for a maximum of 8. A score ≥ 5 is compatible with overt DIC; < 5 suggests non-overt disease. Educational tool — not a diagnostic substitute.
Formula
How this is calculated
Disseminated intravascular coagulation (DIC) is a life-threatening coagulopathy characterised by systemic activation of coagulation, leading to simultaneous thrombosis and haemorrhage. Because there is no single definitive test, the ISTH 2001 scoring system combines four routinely available laboratory parameters into a composite score.
The four parameters — platelet count, D-dimer or fibrin degradation products (FDP), prothrombin time (PT) prolongation, and fibrinogen level — each reflect different parts of coagulation pathology: thrombocytopenia from platelet consumption, raised FDP from fibrin breakdown, prolonged PT from clotting factor depletion, and low fibrinogen from consumption and lysis. Each parameter is scored on an ordinal scale (0–3) based on thresholds published by Taylor et al. (2001), and the four scores are summed.
A total score ≥ 5 is deemed compatible with overt DIC and warrants daily repeat scoring. A score < 5 does not exclude DIC — it may indicate non-overt (pre-DIC) or early-stage disease, and re-testing is recommended in 1–2 days if clinical suspicion persists. This tool is educational; all diagnostic decisions must be made by a qualified clinician in context.
Frequently asked questions
DIC is an acquired syndrome characterised by widespread intravascular activation of coagulation, leading to clot formation in small vessels and simultaneous depletion of platelets and clotting factors, which paradoxically causes bleeding. It is always secondary to an underlying condition such as sepsis, trauma, malignancy or obstetric complications.
An ISTH score of 5 or higher is considered compatible with overt DIC and is associated with significantly worse outcomes and increased mortality. Scores below 5 suggest non-overt DIC; the algorithm recommends repeating the score in 1–2 days if DIC remains clinically suspected.
ULN stands for Upper Limit of Normal — the upper reference range for D-dimer or fibrin degradation products in the reporting laboratory. A "moderate increase" is below 10 times the ULN; a "strong increase" is 10 times the ULN or higher. Always use the reference range from your own laboratory.
Also known as
TG we-Calculate Editorial Team. (2026). DIC Syndrome Calculator — ISTH Overt DIC Score [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/dic-syndrome-calculator
TG we-Calculate Editorial Team. "DIC Syndrome Calculator — ISTH Overt DIC Score." TG we-Calculate. 2026. https://we-calculate.com/calculator/dic-syndrome-calculator.
TG we-Calculate Editorial Team, "DIC Syndrome Calculator — ISTH Overt DIC Score," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/dic-syndrome-calculator
@misc{wecalculate_dic_syndrome_calculator, title = {DIC Syndrome Calculator — ISTH Overt DIC Score}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/dic-syndrome-calculator}}, year = {2026}, note = {TG we-Calculate} }
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