What are the criteria for diagnosing Disseminated Intravascular Coagulation (DIC) in a critically ill adult patient?

Diagnostic Criteria for Disseminated Intravascular Coagulation (DIC)

Use the ISTH Overt DIC scoring system requiring ≥5 points for diagnosis in critically ill adults, or the SIC scoring system requiring ≥4 points for earlier detection specifically in sepsis patients. 1

ISTH Overt DIC Scoring System (Gold Standard)

The ISTH overt DIC criteria represent the global standard for diagnosing decompensated DIC and require an underlying causative condition (sepsis, trauma, malignancy, obstetric complications) plus laboratory confirmation. 2, 1

Scoring parameters:

• Platelet count:

  • <50 × 10⁹/L = 2 points 1
  • ≥50 to <100 × 10⁹/L = 1 point 1
  • ≥100 × 10⁹/L = 0 points 1

• Fibrin-related markers (D-dimer or FDP):

  • Strong increase = 3 points 1
  • Moderate increase = 2 points 1
  • No increase = 0 points 1

• Prothrombin time (PT):

  • ≥6 seconds prolonged or PT ratio >1.4 = 2 points 1
  • ≥3 to <6 seconds prolonged or PT ratio >1.2 to ≤1.4 = 1 point 1
  • <3 seconds prolonged = 0 points 1

• Fibrinogen:

  • <100 mg/dL = 1 point 1
  • ≥100 mg/dL = 0 points 1

Total score ≥5 points = Overt DIC diagnosis 1

Sepsis-Induced Coagulopathy (SIC) Scoring System

The SIC criteria were specifically designed to detect the compensated phase of DIC in sepsis patients earlier than overt DIC criteria, enabling earlier therapeutic intervention. 2 The reported incidence of SIC is approximately 60% in sepsis patients—twice that of overt DIC—and almost all patients with overt DIC were diagnosed with SIC earlier. 2

Scoring parameters:

• Platelet count:

  • <100 × 10⁹/L = 2 points 1
  • ≥100 to <150 × 10⁹/L = 1 point 1
  • ≥150 × 10⁹/L = 0 points 1

• PT ratio (INR):

  • 1.4 = 2 points 1

  • 1.2 to ≤1.4 = 1 point 1

  • ≤1.2 = 0 points 1

• SOFA score:

  • ≥2 = 2 points (capped at 2 even if SOFA >2) 2, 1
  • 1 = 1 point 1
  • 0 = 0 points 1

Total score ≥4 points = SIC diagnosis 1

The mortality of patients with SIC is ≥30%, making this a clinically significant threshold for patient selection for anticoagulant therapy. 2

Critical Diagnostic Considerations

DIC is not a primary disease but a syndrome secondary to underlying conditions. 1 You must identify a causative condition before making the diagnosis. 3

Repeat laboratory testing is essential because DIC is a dynamic process that progresses from compensated to decompensated phases. 2, 1 Serial monitoring allows you to track disease progression and treatment response. 1

No gold standard exists for DIC diagnosis, making clinical judgment essential when laboratory and clinical findings diverge. 2, 1

Common Pitfalls to Avoid

Normal coagulation screens do NOT rule out DIC, particularly in sepsis or subclinical cancer-associated DIC where PT and aPTT may remain normal in approximately 50% of cases. 4

A 30% or greater drop in platelet count is diagnostic of subclinical DIC even when absolute platelet values remain in the normal range. 4 Declining trends in platelet count, fibrinogen, and coagulation factors are more diagnostically important than static values. 4

Hypofibrinogenemia is uncommon in sepsis-associated DIC because excessive suppression of fibrinolysis (via plasminogen activator inhibitor-1 overproduction) prevents fibrinogen depletion. 2 This contrasts with malignancy-associated DIC where fibrinolytic phenotype predominates and bleeding is more common. 2

Screening and Exclusion

A normal D-dimer level effectively rules out DIC, as this test has the highest sensitivity (91-100%) among all laboratory markers. 4 This makes D-dimer the single most useful screening test to exclude the diagnosis. 4

A score <5 points on ISTH overt DIC criteria effectively rules out overt DIC. 4 For sepsis patients specifically, a score <4 points on the SIC score rules out sepsis-associated coagulopathy. 4