How this calculator works
This version follows the British Society for Haematology table dated 18 March 2020, derived from the 2001 ISTH score. It is a dated score implementation, not the revised 2025 ISTH algorithm. Apply it only when an associated underlying disorder is present. In this BSH table, platelets above 100 score zero, 50 to 100 score one, and below 50 score two; fibrin marker categories score zero, two or three. PT prolongation below 3, 3 to 6, and above 6 seconds scores zero, one or two. Fibrinogen at or below 1 g/L scores one. Fibrin marker grading requires the laboratory method and clinical judgement. The result is an estimate for information only and is not medical advice.
Formula
Score = platelet points + fibrin-marker points + PT points + fibrinogen points. A total of at least 5 is compatible with overt DIC. The BSH 2020 fibrinogen boundary is <=1.0 g/L.
Worked example
Platelets 80, a moderate fibrin-marker rise, PT prolonged 4 seconds and fibrinogen 1.5 give 1 + 2 + 1 + 0 = 4. Platelets 40, a strong rise, PT prolonged 7 seconds and fibrinogen 0.8 give 2 + 3 + 2 + 1 = 8.
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Frequently asked questions
Is a score below five reassuring on its own?
No. Evolving DIC may require repeat assessment; the score is not a stand-alone exclusion test.
Why specify the score version?
Published versions differ at some boundaries and in fibrin marker definitions. This tool follows the cited BSH 2020 table exactly.
Can I enter the patient PT instead of prolongation?
No. Enter how many seconds the PT exceeds the laboratory normal comparison value.