What is the Isthmus (ISTH) score?

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Last updated: April 22, 2025View editorial policy

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From the Research

ISTH scoring is used to diagnose and assess the severity of disseminated intravascular coagulation (DIC) by evaluating four parameters: platelet count, fibrin degradation products (D-dimer), prothrombin time prolongation, and fibrinogen level. To calculate an ISTH score, each parameter is assigned points based on specific thresholds. For platelet count:

  • 100,000/μL (0 points)

  • 50,000-100,000/μL (1 point)
  • <50,000/μL (2 points) For D-dimer:
  • no increase (0 points)
  • moderate increase (2 points)
  • strong increase (3 points) For prolonged prothrombin time:
  • <3 seconds (0 points)
  • 3-6 seconds (1 point)
  • 6 seconds (2 points) For fibrinogen:

  • 1 g/L (0 points)

  • <1 g/L (1 point) A total score of 5 or higher indicates overt DIC, while lower scores suggest no DIC or non-overt DIC, as noted in various studies 1, 2, 3, 4, 5. This scoring system helps clinicians objectively assess coagulation abnormalities and guide appropriate management of patients with suspected DIC, which is a serious condition involving abnormal systemic activation of blood clotting. Key points to consider when using the ISTH scoring system include:
  • The importance of accurate laboratory measurements for each parameter
  • The need to consider the clinical context and other diagnostic criteria in addition to the ISTH score
  • The potential for variability in ISTH scores over time, requiring repeated assessments in some cases
  • The role of the ISTH scoring system in guiding treatment decisions and monitoring response to therapy, as informed by studies such as those published in the Journal of the American Heart Association 3 and Circulation journal 4.

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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