ISTH DIC Score — Disseminated Intravascular Coagulation
The ISTH DIC score is an objective diagnostic tool for overt disseminated intravascular coagulation (DIC), developed by the International Society on Thrombosis and Haemostasis.
About
The ISTH (International Society on Thrombosis and Haemostasis) DIC scoring system was established in 2001 to provide an objective, standardized method for diagnosing overt DIC. It uses four readily available laboratory parameters: platelet count, D-dimer/fibrin degradation products, PT prolongation, and fibrinogen level. A score of 5 or higher indicates overt DIC, which is associated with increased mortality and requires prompt management of the underlying condition.
Formula
DIC = Platelets (0-2) + D-dimer/FDPs (0-3) + PT prolongation (0-2) + Fibrinogen (0-1)
The ISTH DIC score is calculated by summing points from four laboratory parameters. Platelet count: >100 (0 pts), 50-100 (1 pt), <50 (2 pts). D-dimer or fibrin degradation products: no increase (0 pts), moderate increase (2 pts), strong increase (3 pts). PT prolongation (compared to normal): <3 sec (0 pts), 3-6 sec (1 pt), >6 sec (2 pts). Fibrinogen: >1.0 g/L (0 pts), ≤1.0 g/L (1 pt). Total score 0-8. Score ≥5 indicates overt DIC with high specificity. The test should be repeated daily or as clinically indicated since DIC is a dynamic condition.
Score Interpretation
The ISTH DIC score is the current gold standard for diagnosing overt DIC, endorsed by the International Society on Thrombosis and Haemostasis. A score ≥5 has a specificity of 97% and sensitivity of 91% for DIC. Early diagnosis is critical, as DIC carries a mortality rate of 30-50% depending on the underlying condition.
Non-overt DIC — 0–4
Score <5. Overt DIC not established. Consider alternative diagnoses or early DIC.
Management: Repeat assessment in 1-2 days or if clinical status changes. Treat underlying condition. Monitor coagulation parameters.
Overt DIC — 5–8
Score ≥5. Overt DIC confirmed. High mortality risk.
Management: Treat underlying cause urgently. Consider blood product support based on bleeding status and laboratory parameters.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| Patients with suspected DIC | 0-8 points | Score ≥5 = overt DIC |
Dr. Mahmoud El-Sayed
Dr. Mahmoud El-Sayed is a consultant hematologist with expertise in hemostasis, thrombosis, and coagulation disorders.
View medical review board & editorial policy →Example Calculation
A 65-year-old patient with septic shock presents with thrombocytopenia (platelets 45), elevated D-dimer (strong increase), PT prolonged 5 sec, and fibrinogen 0.8 g/L. Score: Platelets <50 (2), D-dimer strong (3), PT 3-6 sec (1), Fibrinogen <1.0 (1) = Total 7/8. Overt DIC confirmed.
Related Conditions
Related Medications
Common Mistakes
Using the ISTH DIC score as a screening tool in all hospitalized patients
The ISTH DIC score should only be applied to patients with an underlying condition known to be associated with DIC (sepsis, trauma, malignancy, obstetrical complications). It is not a screening tool for unselected populations.
Using platelet count thresholds inconsistently due to different reference ranges
Use consistent thresholds: >100 x10^9/L = 0 pts, 50-100 = 1 pt, <50 = 2 pts, regardless of the laboratory reference range.
Frequently Asked Questions
What is the difference between overt and non-overt DIC?
How often should the ISTH DIC score be repeated?
References
- Taylor FB, Toh CH, Hoots WK, et al. Towards definition, clinical and laboratory criteria, and a scoring system for disseminated intravascular coagulation. Thromb Haemost. 2001;86(5):1327-1330. PubMed
- Toh CH, Hoots WK. The scoring system of the Scientific and Standardisation Committee on Disseminated Intravascular Coagulation of the International Society on Thrombosis and Haemostasis: a 5-year overview. J Thromb Haemost. 2007;5(3):604-606. PubMed
- Levi M, Toh CH, Thachil J, Watson HG. Guidelines for the diagnosis and management of disseminated intravascular coagulation. Br J Haematol. 2009;145(1):24-33. PubMed