About the ISTH Overt DIC Score
Disseminated intravascular coagulation (DIC) is a secondary condition in which widespread activation of the clotting cascade consumes platelets and clotting factors faster than the body can replace them, producing simultaneous microvascular clotting and bleeding risk. It is always triggered by an underlying disorder — sepsis, major trauma, obstetric complications, malignancy, or severe organ injury — and is never a primary diagnosis on its own. The International Society on Thrombosis and Haemostasis (ISTH) publishes a validated overt DIC scoring algorithm that turns four routine coagulation labs into a single 0-8 point score, giving clinicians a reproducible way to track whether a patient's coagulopathy pattern is consistent with DIC.
How the score is calculated
The ISTH algorithm first requires that the patient have a known underlying disorder associated with DIC — the score is not validated for use outside that context. Four components are then each scored and summed: platelet count (>100x10^9/L = 0 points, 50-100x10^9/L = 1 point, <50x10^9/L = 2 points), a fibrin-related marker such as D-dimer or fibrin degradation products (no increase = 0, moderate increase = 2, strong increase = 3), prothrombin time prolongation above the laboratory control (<3 seconds = 0, 3 to <6 seconds = 1, ≥6 seconds = 2), and fibrinogen level (>1.0 g/L = 0, ≤1.0 g/L = 1). The four component scores are added together for a total ranging from 0 to 8.
Interpreting the total score
A total score of 5 or more points is considered compatible with overt DIC; the original ISTH validation recommends repeating the score daily in that case to track trajectory. A score below 5 is suggestive of, but does not rule out, non-overt (compensated) DIC, and the criteria recommend repeating the panel over the next 1-2 days if clinical suspicion remains high, since early DIC can evolve quickly. Because the fibrin-related marker categories (no/moderate/strong increase) are assay-dependent rather than fixed numeric cutoffs, laboratories typically calibrate "moderate" and "strong" thresholds to their own D-dimer or FDP assay.
Educational Use Only
This calculator reproduces the published ISTH scoring rubric for educational and reference purposes. It does not replace clinical judgment, does not diagnose DIC by itself, and should never be used to make treatment decisions without a licensed clinician reviewing the complete clinical picture, trend of repeated labs, and the patient's underlying condition.